Promo removed

This is a complain for a promo removed from my account. I received the $300 promo to buy a watch and after I received my watch and pair with my phone the promotion was applied for the first payment cycle and then was removed. Today I found out that I supposed to activate my watch in 30 days, I thought that I did it once I received the watch and paired with my phone following the steps included in the package, well, didn't happens and the watch was not activated, so I did it today (3 days after the 30 days) but when I called they said that I lost the promotion because I didn't activate the watch in 3o days, and they can't do anything about it so I will need to full pay the watch. This is outrageous. Why I didn't received any email or notification warning me about this? One more time, I thought that I activated the watch once I paired it with the phone following all the instructions. Why they removed the promo after they applied it the first cycle? Why they can't applied the promo? Either way the watch was activated, 3 days after but it is activated. If the promo can't be applied, shall I disactivate the watch? Shall I, after more than 10 years with them, move to a different company? I hope someone can help me with this because nobody was able to do it by phone.