Welcome Alberto,
Are you saying you and/or your son are capable of safely renewing brake pads? It seems you have already bought replacement pads.
Since the seller seems disinterested in sorting it out, why not carry out your own assessment of the remaining brake pad thickness, and simply renew them - since you have them.
Worse possible case:- brake pad wear light remains on after you have done that -? Worry about sorting that out when you get to that point.
Perhaps you could let us know how you get on.
Kind regards,
Gareth.