Refuses to assist

Mtn refuses to help me with a Sim swap, first time I received a sms saying I should get a new Sim card and then do the Sim swap, got a new one tried and it kept on saying technical error please try later after trying later, multiple times, it now says I've exceeded my tries but Mtn has been giving issues on giving me the chance to do a Sim swap on my own and now I have to go to the store and pay for a Sim swap