I had an issue where my daughter received an email about the plan after the first month trial.
She is 12 years old and did not understand the necessary actions to be taken. As a parent I did not, nor did my wife, received any updates about the subscription and or communication between BUNQ and our daughter. The issue was handled correctly by BUNQ after reaching out but the flaw remains.
So In my opinion this could be fixed easily to include parents/guardians in all communication with the minor.
Secondly, a certain degree of control over the plan and or features of the minor account would also be good idea.
Apple does the same with child accounts, parents can grant or deny features to the child account in order to protect them and or discus the level of freedom with the child.