i use
Nokia 1600 as extra in hand phone ,, and my main phone is nokia 6681 , with which i use,, mobile internet and phone calls,, i have experienced all these problems.. and found the problem happens mostly,, when we interchange the sims.. multiple times. all it takes time to update the phone model with sim,, at the server side of the telecom company,, also.. one more problem, is,, when ever we change our sim,to our mobile phone,, it sends messages,, but it asks,, you,, when there is mostly outgoing sms problem.. for this, you have to go to message settings and there. the out sms number have to be configured correctly according to the company telecom u are connected to,, you can get the sms out number from calling mobile help from customer care also..,, this is what actually happens,, to my understandings.. i solved my issues. by the same manner ......in back times..,,,now i can work with any sim.. without having issues..