Incorrect outstanding amount and SMSes

I received about three SMSes regarding outstanding amount as well as costs that I am incurring due to usage limits. When I phone 808 to query this I am told to ignore the SMSes and that there is no incorrect amount or extra costs on their system. Yet, I received and SMS again and the outstanding amount on the Internet is still incorrect. It takes my time to phone 808 and hope that someone will answer before the second coming and then I am told to ignore the messages that comes from MTN. What is going to happen when I receive an SMS that I should give attention to but I ignore it, because that is what I have been told? Has MTN's system been hacked? Why do I receive incorrect messages?