Never pay more than you have to ...

Recently we payed to O2 by mistake more than was written on the bill. You might think that everything is ok, next time we will pay less, but O2 is not so smart and they didn't recognize our payment and send us a remainder! After exhausting explanation they noticed the payment and everything seemed fine. This was not the end because this time they asked us to pay 40CZK for the remainder, which was unsubstantiated! It takes 30mins call to their infoline to explain them that we will never pay this just beacause they have stupid system. After two days they decided that we are right and we don't have to pay that - happy days :)