NOS - Unexplained charges

Because of Nos. error in not adequately providing internet service for 6 days in our apartment, which caused us not to work during these days, we are still asked to pay the full amount as our monthly charge. we have called several times to no response; instead, we were charged 107.48 euros for payments that was not outlined or explained to us . I have been to their store, and they corrected 15 euros for a false charge and refused to correct the other additional expense. I have even asked them to reverse the date payment date from 4th of next month to the previous date of the 19th of this month. Nos has refused and insisting I must pay for internet service that I have not used . its been a very very very frustrating experience with Nos affecting