Poor service

With Autoapge closing down, all its cellphone contracts have been transferred back to the main cellphone service providers. My contract was moved to MTN. I have a query on my latest statement which is from Autopage. I called the number on the statement and I was transferred to MTN. When I punched in my cellphone number on the MTN site, I got a message saying that the number is invalid. Surely both these companies should have ensured there was a smooth transition from Autopage to MTN? Is this perhaps a ploy to fleece the customers off again as my bill is unusually high? Both companies have very poor customer service and now the problem is compounded!