Who I have the same questioned this topic

Saw this online-only promotion on Verizon website back in August, pretty good deal. Basically buy a new IPhone 11 Pro Max with a new premium plan, you get $450 credits plus a $150 rebate giftcard. I was happy with the deal and bought a new Iphone 11 pro max on Verizon website, and switched my wireless plan from AT&T. Everything goes well, except they didn't show up in my bill. Called in several times, all agents talked nicely, and assured me that everything is alright, and it will appear in my bill after 3 billing cycles. Never happened. Called in again, now told me that there was no such online promotion. 
Besides this, I also traded in my iPhone 7, with a promise of $600 value, but only get $125, called in also, the rep also told me that it's adjusted back $600 and the credit will appear in my bill after 3 billing cycle. Which also never happened. 
I'm speechless about Verizon's practice, won't trust them anymore. No business integrity at all.