Don't receive the service one pay for.

I've been a customer with Snowball for nearly 3 years and service was always good. But recently I receive sub standard service from them. I pay a full a amount every month, but don't receive the service that goes with it. For 9 months this issue has been going on and no one has been able to sort it out or get back to me to what the actual issue could be. I'm only with them cause I don't have another alternative. Which is the worse scenario to be in...