Hi ​@GloriaChauvet do you mean that you have taken the modem with you to France and you're trying to send the modem back from there? We provide free returns from within the Netherlands but this does not apply to outside of the country. In this case it seems more profitable for you to not send the modem back, as the fee for not returning the modem will be € 75. 

All right. But if I couldn't send the modem back, I'm going to be charged, even though it's not my fault. I have to go to the Netherlands on December 12. Can I send the modem back on that date to avoid the charges? 

​@GloriaChauvet You can use any courier, you not need to use DHL, maybe cheaper, from abroad to NL costs around 20,-€. But a 'antwoordnummer’ address is a POSTNL address en is valid in the Netherlands. From abroad often you can't send to this kind of adress and you need to pay for the returning from the Netherlands. I know that DHL refuses to deliver to a 'antwoordnummer’