$150 T-Mobile Home Internet Rebate Scam

I switched my three lines carrier to Tmobile with a promise to getting a rebate of $600 for the three after three months of service. I switched in February and waited till June and nothing happened and I went to the T-Mobile store and was told that only one line was approved and that the remaining two lines were registered as being originally a T-Mobile line and not switched to T-Mobile. I was so mad because that was my daughters lines and threatened to withdraw from the service and they promised to now pay me $400 instead of the $600 which I refused insisting on getting what was agreed on. After a long discussion, they approved it and gave me $200 and that $400 will be sent later on the same week. I used the $200 for purchase and was declined several times and the remaining $400 was NEVER sent. This is T-Mobile gift card is a total SCAM. I regretted wasting my time and money with T-Mobile and I should have remained with AT&T but am canceling the subscription if it means losing the lines.