Complaint - I cancelled the contract, but still was charged!!

Dear Sirs,

I was in Heidelberg from 1 September 2015 to 15 February 2016 for 6 months of Erasmus studies as an international student from the University of Athens.

On 7 September 2015, I bought two internet usb sticks from the O2 shop at Hauptstr. 118, and the employee Mr. Kxxxx asked me to come again in February to cancel the contracts before I leave.

Indeed, on 8 February 2016 I went, I returned the sticks and gave a paper from the studierendenwerk, proving that I leave Heidelberg. Mr Kacar later sent me an e mail, confirming that he cancelled the contracts. Indeed, the automatic payments from my bank account stopped and I could no more login to MyAccount.

A few days ago, after so many years, a letter came in Greece from COEO Inkasso, stating that I owe 712.82 euros to O2 (Telefonica Germany) !!! Half of the money concern a mobile device I never bought!!!

I called both O2 and COEO Inkasso, they say that they never received anything from the shop (“yes we see something changed in February 2016, but the contracts were not cancelled”). They don’t accept the employee’s e mail: If I don’t have an official paper, I have to pay. Also, the COEO Inkasso warned me that if I don't pay until the 15th of September, they will sue me!!

The shop employee Mr. Kxxxxr confirms that he has sent everything to O2. A friend visited the shop yesterday, Mr. Kxxx is still there and confirms all the above. When asked to call O2 and COEO Inkasso, he said that they can call him.

Why is this happening? How does this make sense?? I did everything on my part to cancel the contracts.

The employee's e-mail is available and I can send it to you through PDF, if you like.

Kind regards,
Georgios Mitropoulos

Edit o2_Flo: No real names pls