False advertising

I was contacted by rain with regards to them assisting us with upgrades from 4g to 5g as its a promotion running in their side and I asked if I'd have to pay any additional money and was advised that I would have to at that time I wanted to cancel my contract however opted to stay to see how things would work little did I know that when it's time for them to debit my account they would debit more than what I agreed on and was paying and I'm not adki myself why I bothered to give them an apportunity to redeem themselves if they now want to rip me off.