No help from MTN

I discovered last week Friday that my cellphone is unable to receive calls from other networks except for mtn numbers, i contacted the call centre on 135 and they reset my number and told me to switch of my phone but it still didn't help, i phoned the 135 number again and they gave me codes to remove barring and forwarding/divert it still didn't work, Subsequently i went to an mtn shop and the lady there gave me an mtn book and told me to dial the numbers in that book and still didn't work, i then phoned the call centre of which the lady then opened a ticket with ref nr *** on Saturday i even thought i should go do a sim swap, when i got to mtn they said because there's an open ticket they cant do a sim swop, i was basically without a phone this weekend because all my phone can do is send sms and make calls but can't receive calls except from mtn numbers what's frustrating is that it doesn't look like mtn knows how to solve this problem because even if i put my sim card in another phone the issue persists so clearly its a problem with the mtn sim card its really frustrating I'm even thinking of canceling my contract and porting my number.