Almost assuredly, no. AFAIK, the only exception is if you are under contract with a 3rd party retailer. T-Mobile proper has no contracts.
When you cancel, do so near the end of the billing cycle, as your final month of service will not be prorated.
Are you buying your phone on an EIP? Partial months are not prorated, so try to port out just before the end of your service month.
First off, we do hope you'll keep your service with us kjbxpress. It'd be sad to lose you. As mentioned above, there's no contacts with T-Mobile so there shouldn't be any termination fees charged from us.