Renewonline cheating people

I needed to renew my license end of March, but since the Post Office had already closed by then for the lockdown, I decided to use Renewonline. I went through the process and paid the full amount on 1 April and sent them proof of payment. That was the last I ever heard from them. Last week, more that 3 month later, no disc and no word from them. After sending several enquiries, the admin person finally answered: "Unfortunately the amount for this renewal is no longer the same as there is penalties and arears for 2 extra months and your expiry date will change to June 2021. If you would still like to pay this renewal through us kindly make a payment of the outstanding amount of R316.00 to our Renewonline bank account listed on your profile". How can they charge extra after I have already paid 3 months earlier, also considering that the government has changed the renewal deadline to September? I requested them to refund me, and you guessed - no response :-( This company is cheating people. DO NOT USE THEM!!!