incentive reimbursement

Hi - I have been trying to get my incentive reimbursement for weeks. I have had several chats online and on the telephone. It caused me a financial need for paying off T-Mobile in order to receive the incentive and change carriers from T-Mobile to Comcast which I will make sure no one else changes to Comcase after my stressful ordeal. I loved T-Mobile but was offered an incentive to consoliate internet/mobile service. I am supposed to receive $600 ($200 for 3 phones) I was originally told I would receive $500 for just my phone, but the salesperson was not correct in offering me this amount. I was told by another salesperson that I would only receive $200.  I had to pay off two phones on my T-Mobile account in order to switch carriers. Mind you, these two phones were FREE with T-Mobile if you continued with their service. After receiving their commission, the salesmen were no longer interested in helping me with my reimbursement. The location I visited was Highland Avenue in Salem, MA.  I really need to replace this $600 back into my budget to pay my bills. 
Thank you. 
Marion [Edited: "Personal Information"]