Cannot receive phone calls from MTN numbers

Good day,<br> <br> I am on a contract with Cell C. I cannot receive any phone calls from MTN numbers.<br> I have had the contract for more than a year now and no one has been able to assist me.<br> I have been to the shop on numerous occasions and have contact the call centre, but with no luck.<br> Each time I was given a list of codes to type in on my phone, but these did not work.<br> <br> I have also been paying the full price on my contract. A lot of my friends and relatives are on MTN and none of them are able to reach me.<br> <br> Any help regarding this will be greatly appreciated.<br> <br> Regards,<br> Riaan<br>