Wife's account payment linked to Spotify partner "Base" - how to disconnect?

[TonioRoffo]

Wife's account payment linked to Spotify partner "Base" - how to disconnect?

My wife started out on spotify premium using a cell phone plan from the Belgian operator "Base" which included spotify.

The plan is now changed to a cheaper one and we have disabled Spotify as an option, in the Base portal.

However, one month later, when checking the Spotify account, it is still reported as linked to Base:

(Dutch interface):

"Jouw abonnement is gekoppeld aan onze partner BASE company.  Benader BASE company voor vragen over je abonnement"

-

"Your subcription is coupled to our partner BASE company.  Approach BASE company for questions about your subcription"

However, BASE support has absolutely no clue what is going on.

What I would like to achieve is to couple this Spotify Premium account under my family plan.

Please advise on how to proceed.

Thanks!