Money debited without authorization

Mobisos called me for a phone contract and asked for my full details. I provided simple because when you looking for a contact you have to give your details, after that they wanted me to accept their debiting on my bank account, I didn't accept as I couldn't understand what was the R140 they wanted to take off for. Today they debited that R140 which I still don't know what it's for, and worse I never allowed them to debit, I never even received a call for that contract whether it's approved or not. I went on few social media to see their reviews and apparently am not the only one who got their money debited without giving them authorization. Mobisos this is very wrong it has created a very bad view about your business.