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Old May 16th, 2012, 11:54 AM   #1 (permalink)
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Sad Sprint unlocked phone not working on T-mobile

Hi,

I bought a Motorola Android unlocked phone on ebay (don't have the model number handy right now.. will post it later). The phone worked with a GSM SIM in India. I landed in US and got a T-mobile SIM. This SIM is working in a simple feature phone which was bought unlocked directly from Nokia.

However, when I put this SIM in the Motorola, I am not able to make any calls or access the internet. I can see the mobile network signal which shows 4-5 bars most of the time. But, when I try to make a call, I get a message saying 'Your account could not be validated. Please call customer service. Message 5 Switch 540'. The Motorola shows 'Unlocked phone' at the top left upon booting, so I guess the bootloader was unlocked. Because, it has worked fine in India, I guess the SIM should also be unlocked.

My best guess is that it is still trying to use Sprint network despite having a t-mobile SIM. I am very new to Android, locked phones etc. It would be great if you can help me figure out the problem and help me fix it. Can I contact T-Mobile and ask for help? Will they help in this case?

Thanks,
Sunil

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Old May 16th, 2012, 12:19 PM   #2 (permalink)
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Sprint is CDMA network, GSM phones won't work on CDMA carriers and CDMA phones won't work on GSM based carriers. You can't use a sprint phone on Verizon either even though they're both CDMA networks or vice verse.
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Old May 16th, 2012, 12:33 PM   #3 (permalink)
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Sprint has also alwaus had a different channel than T*Mobile. T*Mobile uses 1900MHz GSM whereas Sprint used to be 950MHz PCS last time I heard. The phone may be hearing (and indicating signal from) a Sprint tower, but Sprint won't validate a T*Mobile account format.
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Old May 16th, 2012, 01:25 PM   #4 (permalink)
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Originally Posted by timelord65 View Post
Sprint is CDMA network, GSM phones won't work on CDMA carriers and CDMA phones won't work on GSM based carriers. You can't use a sprint phone on Verizon either even though they're both CDMA networks or vice verse.
Thanks timelord. I was able to use this phone on a GSM network in India. I was able to call, receive calls and text people. But, I guess it asked me to switch to 'Global mode' while searching for networks
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Old May 16th, 2012, 01:30 PM   #5 (permalink)
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Thanks lectraplayer.

Quote:
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Sprint has also alwaus had a different channel than T*Mobile. T*Mobile uses 1900MHz GSM whereas Sprint used to be 950MHz PCS last time I heard.
Is there an option to force Android to use a particular frequency?

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The phone may be hearing (and indicating signal from) a Sprint tower, but Sprint won't validate a T*Mobile account format.
Yes, I also suspect this. But, I am not able to understand how does my phone know that it can contact Sprint. Is it simply based on the frequency at which it's operating? If so, I guess I can get it to work by changing the operating frequency.
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Old May 16th, 2012, 03:55 PM   #6 (permalink)
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Is there an option to force Android to use a particular frequency?
No there is not. Sorry. If the phone's radio doesn't support a certain frequency (in this case 1700/ 2100 for 3g HSPA, and 1900 for 2g edge), then there is no way of it to ever support that frequency.
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Old May 16th, 2012, 05:46 PM   #7 (permalink)
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No there is not. Sorry. If the phone's radio doesn't support a certain frequency (in this case 1700/ 2100 for 3g HSPA, and 1900 for 2g edge), then there is no way of it to ever support that frequency.
The phone model is Motorola MB855 (Motorola Photon 4G MB855 - Full phone specifications). The specs say it supports the frequencies mentioned above
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Old May 16th, 2012, 06:43 PM   #8 (permalink)
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Originally Posted by sunilpadda View Post
The phone model is Motorola MB855 (Motorola Photon 4G MB855 - Full phone specifications). The specs say it supports the frequencies mentioned above
So it seems, like most global phones, it won't work on US GSM carriers... Idk if there is any way to make it work on a US GSM carrier, and I'm just on break at work right now so I don't have time to see if there is a way to make it work. I can try and find out more about it, when I get off work if I remember.
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Old May 18th, 2012, 10:28 AM   #9 (permalink)
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Originally Posted by marc12868 View Post
So it seems, like most global phones, it won't work on US GSM carriers... Idk if there is any way to make it work on a US GSM carrier, and I'm just on break at work right now so I don't have time to see if there is a way to make it work. I can try and find out more about it, when I get off work if I remember.
Thanks marc
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Old May 19th, 2012, 10:35 AM   #10 (permalink)
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I am fairly certain there should be a way to use the gsm.

Check under settings for an option to switch from cdma to gsm. I have read this is possible with Verizon world phones by just changing the settings.

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Old May 19th, 2012, 10:50 AM   #11 (permalink)
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Android really doesn't handle the frequency or the GSM, CDMA, or anything. It just sends its requests to a special chip on the phone's radio tranceiver. Change that chip and you can now go on any network the new chip supports. The easiest thing to do, though, is to drop into any T*Mobile and nab you a MyTouch. Phones are hard to solder on without destroying them. If there is a setting to change networks, the chip in your phone has a function that lets it switch and the manufacturer told Android how to use it. There is no such function on most phones.
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Old May 19th, 2012, 01:32 PM   #12 (permalink)
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Quote:
Originally Posted by Sevreth View Post
I am fairly certain there should be a way to use the gsm.

Check under settings for an option to switch from cdma to gsm. I have read this is possible with Verizon world phones by just changing the settings.

-Sev
It's not that easy... Global phones from US CDMA carriers ignor US GSM carriers. There is a way (if it is a software limitation) to change it at the kernel level from what I have read, but no one has done it/ tryed for the Photon. So basically there isn't really a way to us it on US GSM carriers.
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Old May 19th, 2012, 07:38 PM   #13 (permalink)
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I think it's more a hardware issue than a software issue. All Android has to do is just send and receive the data and the radio circuitry gets it to "the network." If a CDMa device gets something from a GSM network, the OS never hears it to be able to filter it.
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