Travellers entering a country have a 'tax-free' allowance - within which they can import goods free of taxation. Customs charges are set and imposed by the relevant Customs Authorities in the event that you (or one of your party) are found to be in excess of your import allowances. AirPortr has no influence or visibility of the actions and determinations of Customs authorities.
When these charges are imposed, they must be paid on the spot in order to release the bags for onward delivery. For that reason AirPortr will pay charges on your behalf (up to a maximum of CHF300) to ensure your baggage is still delivered seamlessly to you. These charges are automatically recouped from your payment card. AirPortr does not charge a service fee when this occurs.
In the event that you're required to pay import charges in excess of CHF300, AirPortr will contact you and you will need to liaise directly with the Customs Authorities to arrange payment and regain custody of the bag(s) in question.