I find that if I'm in a weak signal area, I won't get the call, but I will get the text messages that tells me I've missed the call. I found this on both my N97 Mini and my DZ. It's really annoying... I can make the call back, even though I'm still in the same area. I'm on Orange and have noticed all sorts of strange things happening with them lately.
It could also be a capacity issue. You might have a good signal but the cell is overloaded with traffic. This might not stop your data, but it might effect calls.
I've seen this happen on very overloaded temporary sites. Calls don't get through but data and texts do... I've also seen it the other way around. I can make call, but not use data or texts.
I doubt if it's a settings problem.
I guess that it could be a firmware issue. Maybe the phone isn't polling the network as often as it should. Great for battery life, but not so good if your missing calls because of it.

 

I'm not sure we can... If it's a network issue there's nothing we can do.
If it's a polling issue, we'll just have to wait for upgrades.

The networks are struggling to keep up with the demand for data. This coupled with the number of new phones hitting the networks every day only adds to the problems.

On really busy cells, switch off GPRS and revert to GSM. The GSM network have plenty of capacity. GPRS is used to make calls as well as carry data. GSM is only for calls. I used to have to turn GPRS off when connected to overloaded temporary sites. How you turn GPRS off on an Android I am yet to find out... Someone might be able to help... I can do it on Nokias, but that's not a lot of help here Hang on... Just tried it...
menu, settings, wireless + networks, Mobile networks, network mode, GSM only.
Try it. it just might work