We had been with Sprint for many years on an employee plan, which was similar in price to the TMO plan. What finally motivated us to switch was the "Tax Time Switcher" (or something) promo that offered a $150 per line if you port from another carrier.
We made the switch early Feb 28 (the last day of the promo) and our new sim cards were in the mail that same day. The reps told us that even though we wouldn't get the sim cards until after the deadline, since we had signed up and paid for sim cards, we were still be eligible for the promo.
Later that day, my sister and brother in law heard what we did and decided to get in while the promo was still available. We called again and had two more lines added to our account, but the rep said our account was still being created so she would call us back in a couple hours when that had completed. Well, she never called and we ended up having to wait a while before they would let us add the lines. Because of this, our 3rd and 4th line were added after the deadline.
We talked to a rep to make sure at least the first two lines were eligible, and he said yes, the two $150 cards would be arriving within 6 weeks.
Flash forward a couple months. We get a text saying that we were too late in switching, so we wouldn't be getting the $300 that motivated us to switch in the first place! And this is after accepting that we were only getting the promo for 2 lines instead of 4, which would have happened if the rep had kept her word.
One reason T-Mobile may think we were too late is that the rep that ported in our 3rd and 4th lines did so over top of our first two numbers. Lines 1 and 2 had the wrong numbers, and lines 2 and 3 had no service. That took days to sort out, and left all 4 of us with no service for a couple days. To fix it, a rep told me they had to add all new dummy numbers and match each sim card to the correct phone. Maybe our promo was tied to the original dummy lines?
Every time I call support, they fix nothing, but manage to mess up our bill for unknown reasons. So far they have managed to remove our "this one's on us" promo and unenroll us from autopay, and although the plan is fixed, we have overpaid a couple times. This is my next attempt at getting the situation resolved. So far, not a good experience with T-Mobile.