what was the transaction size? i doubt is really 7 euro and 7 euro is like 350k satoshi at the moment, which is like you are sending a TX of 1300 bytes, if really is true, try to use an accelerator next time
Since Op hasn't shown us his BTC transaction ID and I doubt that there is a company which is accepting bitcoin directly.
So since some kind of bitcoin payment operator is included in this equation, the most likely scenario is that there was some kind additional fee associated with this TX.
Sometimes (way more often than you even think) there are multiple fees associated with sending money online.