Usenext charged for unused access, now adding arbitrary charges to my 'debt' - ignored my response Germany

I am writing this report both to warn other people of Usenext's practices and to, hopefully, get some sort of meaningful response from them, as I see that they have responded to other people's reports on here.

 I used their services for several months recently, their software worked reasonably well with only a few hiccups which seemed to clear up.  Then the software stopped working, the search worked but nothing would download.  I waited for a few days and tried again but, this time, the problem did not clear up.  I tried uninstalling and reinstalling it to no avail.  I then decided that I did not want to attempt to use it any longer so I uninstalled it and cancelled my recurring payment to Usenext through Paypal.

 All seemed well for a while, then I received an email telling me that I owed them money for their services (I had been paying monthly).  I replied, stating that I had not received any services for the period in question, had not attempted to access them since and had removed their software and cancelled my payments.  Apparently, this was not enough - I should have cancelled with them too.

 I argued that, as I had not been able to avail of their service during this period (a fact they should easily be able to ascertain) due to a fault in their software (indeed, I only cancelled my payments due to the software not working), they should drop the charge and call it quits.  They did not agree.  We argued back and forth to no avail.  I then received an email telling me that, on top of the 9.95 euros that they said I owed them, they had added fees amounting to a further 11 euros and that they now wanted 20.25 euros!

 Shortly thereafter, I received a letter from something called Teschinkasso, apparently acting for Aviteo limited (Usenext), who said that I owed 23.82 euros.  Not wanting a long-running saga, I emailed Usenext, stating that, although I did not feel that they were entitled to the original 9.95 euros as I had not been able to use their service, I would consider paying it to finish this thing but that I definitely did not agree with the extra money that they were asking for (a figure they and their collection agents did not even seem able to agree on!).

 I received no reply whatsoever from the company in response to my attempt to bring this to a conclusion then, on Friday 11th October, I received another letter from Teschinkasso, citing 'damage' caused by my delay and adding a further 25 euros to what they claim I owe, quickly bringing a 9.95 euro 'debt' up to 48.82 euros!  They also give a deadline of 20th of this month and threaten further charges and legal action.  This is a despicable way to deal with customers, it also gives virtually no time to try to sort something out with Usenext (even if they would respond) or get any proper legal advice as the deadline is so short; they are effectively trying to frighten and hustle me into paying these rip-off charges.

 They also state that the only method of payment they will accept is bank transfer, which would add even more to the costs!

 I would be interested to hear Usenext's justification for what they are trying to do to me, the outlandish increases in the account and for the aggressive and intimidating tone of the letters sent to me by their chosen collection company.

 I would also like to know if they feel that this is the way that they should be treating their customers, especially ones who have paid for their services on more than one occasion (I was a paying customer at least once, possibly twice, before the period in question, several years ago).