Reversed airtime doesn't pay borrowed Airtime not fair

I loaded R100 airtime, cellc debited R20 from my account, I wanted to buy R99 minutes, they forced me to borrow the outstanding R20. Cellc loaded subscriptions on my phone that I didn't sign up for, they then reversed my airtime. the reversed airtime didn't count as a payment for the airtime borrowed, the call center didn't help either