Thank you, Oreste, for your response. I have meanwhile found contact with support at https://twitter.com/SpotifyCares.
- "Both your country settings and payment method have to match, so if you're currently located in Colombia, you'll need a Colombian payment method to subscribe."
No, that's not correctly formulated. I don't need a Colombian payment method, because I'm located in Colombia, but because my profile is Colombian. Spotify does NOT verify my location, that is actually the whole problem.
I understand that Spotify needs to determine the location because of the user rights of the available music. Spotify CHOOSES to do that by verifying the billing address of the payment method. That means I personally can choose between a Dutch, Spanish and Colombian payment method as I wish, because I have bank accounts in these 3 countries. And hey, I might even open a Swiss bank account or request a credit card in the USA. So in other words: the method to verify someone's location through his payment method is not waterproof.
A more effective method to verify the location might be tracking the ip-address, but Spotify probably has trouble with people spoofing their addresses. So I do admit that determining the actual location is really hard and Spotify's method probably works in 95% of the cases.
- "Spotify will only charge the price of the promotion/monthly subscription, any additional fees are up to your financial institution. Some banks might charge an additional fee for international transactions."
My Colombian bank does NOT charge additional fees. Spotify uses a international payment provider, an intermediary, named Safety Pay. It is Safety Pay who charges an additional fee of $ 2 for every transaction below $ 50, not my bank. I buy a lot through internet in Colombia, Europe, and the USA, and Safety Pay is the only payment provider I'm aware of that charges additional fees. I do not know if Spotify is aware that Safety Pay charges extra, if they do, Spotify should mention that clearly before redirecting me to the payment system.
One issue that isn't solved yet is why I'm not charged according to the offer of 3 months. The guys at https://twitter.com/SpotifyCares checked and confirmed me I'm eligible for the offer.
[So no: problems not solved yet.]