I never received my 500.00 Gift card

I never received my 500.00gift card for switching from Verizon to Xfinity. This is the whole reason I even signed up for service. Now my bill has gone to collections. How are you going to fix this. I spoke with someone and they advised all was well and I should expect my card in two weeks... Nothing then I spoke to another associate that advised they never received my documentation went to Verizon had them print out the whole bill and emailed it to a special email that they gave me... Nothing. This is not right. I have went above and beyond to do my part and you guys give us the run around. I called today they told me they had a 200.00 gift card for me and sent that virtual.. Thank you but the promotion was for 500.00 so that I could pay off my phone I had a new I phone 15 it was worth 800.00 dollars. What are you guys doing. I never would have switched . It messed with my credit. It has caused me more grief than anything.