Not getting hold of MTN

I app**** online for a contract however I used my capitec bank account which is still on my married surname, I was concerned that this may be an issue but the lady told me to do so because I recently changed from my 10+ year bank to another bank and the account is open less than 3 months. I received an sms to say that the authentication failed and I should chat to the agent. no one has called me back or I am not getting through to MTN to understand and resolve so we can continue with the application.