How does Verizon get away with 'offers' and then charge a higher amount???

In September I bought an iphone 7 on a 'special offer' of $5 per month for 2 years.  The normal monthly charge was $16.66 per month.  Three months later, I'm still being charged $16.66 per month despite being told it would be changed.  Have others had this problem?  

I would suggest others beware of this practice by Verizon.  I think it is a ploy to see if customers will get tired of calling them, and just pay the original price.