No 3G Coverage

i am using a Sony Experia C 2304, last two days i lost 3G connectivity on my phone and when i phone the customer service i was asked to restart the phone several times to which i did and was told to take the battery out and the SIM out which i did and nothing is working still, when i ask that i speak to the technical support of MTN so i can get the APN settings for my phone the fone rings and cuts off after few minutes, i have tried to contact MTN for the past two days and i am still not getting any joy, i am telling you if i don't get this sorted out my only options now will be to port my number to another service provider as being on MTN does not help. i now have opted to get another card of Cell C when i want to chart via whats app i insert the SIM and then take it out afterwards, this is becoming rather irritating