It is impossible to get help

MTN took over the Nashua Mobile book last year and since that happened I have had untold problems. I keep on getting suspended as they have lowered my credit limit by 75% (I have never missed a payment in my life). The only way to get this changed is through the call centre and it is impossible to get help. Literally 90% of the calls just get cut off when asking to speak to an agent and if it does hold your call no one answers - I have held up to half an hour with no pick up. The one and only time that I finally spoke to someone they put me through to credit who said they would send me an email with what I need to do - the email was never received!!! I am not sure that I have ever dealt with worse service in a situation where I am trying to buy more of their services.