Very bad service, slow internet speeds

How can a business charge me a full month amount for less than 7 days services? I bought my sim on the 16 which was not activated until a week later on the 24th but I just recieved an email informing me of a pending payment on the 1st July , what happened to pro rata pay or service it’s very suspect business practice what rain internet is doing having to pay full month amount for 7 days service. It’s very difficult to engage them on these issues that are not available