Unconstitutional

Unfortunately Mweb is point of sale so they get the review. When you go to Shoprite, PNP, Checkers, Spar etc and do your monthly groceries shopping , they do not come to your house at the end of the month and take back the items not utilized and they also do not charge a fee if you would like to roll over the items not utilized so why are the service providers doing that as we pay a fixed fee for a certain amount yet I utilize 50% of my data on a monthly basis as I receive emails from mweb stating this fact. I should then pay for what I use or it should be rolled over into the next month. Hense why I have not made payment the past two months.