Unfair overcharging by Webafrica

I have been a customer for years. product ok. i wanted to cancel 1 July with 1 month notice but was forced to pay until end of August. a month is 30 or 31 days ?? for Webafrica it seems to be 31. Close to highway ******* i think as I wont use their service from 1 July but will have to pay 2 month non use!!!