Hello kimkimtravel
I am saying that the luggage transportation service is offered to people who want to travel from A to B using public transit but who are not able or willing to transport the luggage themselves on the train and therefore want SBB to take care of the luggage. Therefore, at luggage check-in, the customer must be in the possession of a valid ticket for the same route for which they want to send the luggage. This is verified at luggage check-in.
If your customers are intending to do the Haut Route by ski / hiking, they likely do not have a valid ticket to travel from Verbier to Arolla by public transit. And, SBB will refuse the luggage transportation as the railway company is not a private luggage transfer company. In this case, you must hire a private luggage transport company, there are quite a few offering this service to people doing the Haut Route. Google does know them.
Kind regards,
Roland