Thanks for your response. Yes I do mean Virgin Mobile, I have a pay monthly SIM. I have no problem sending or receiving SMS or MMS and the internet works fine. It's just if I do not use my phone for a while, say overnight, I have to acknowledge 10 - 20 messages of (Sorry the sending of text messages to this number is not possible). These appear without any actions being performed on the phone.
I have my APN Settings as follows
Name: Virgin
APN: gotovirginmobile.uk
Proxy: 193.30.166.003
Port: 8080
Username: user
Password: <not set>
Server: <not set>
MMSC:
http://mms.virginmobile.co.uk:8002
MMS proxy: 193.30.166.002
MMS port:8080
MCC: 234
MNC: 30
APN type: default
Thanks again for your response. Any thoughts or suggestions would be really welcome as this is driving me mad!