****med by Rain Internet Service Provider

Registered internet service for r479 per month,I was last active on the account in March,since then I was not using the their internet service,so today i decided to reconnect my account with them and I wanted to change my payment date from the 15th of each month to 25 of each month,they asked me to pay first,and they charged me r510.I tried to change my payment date I couldn't do it myself on my account rather they send me an email that tehy already changed it to the first of July which I never asked them to do and they are now telling that on the first of July again they will charge me a full amount to pay which is not fair it means they ****** me of my r510 just to use for 3 days.im very much disappointed and I'm going to cancel my contract with them,they are ********