It’s best to open a fault ticket with BMW and Swisscom and be persistent, i.e. demand that the two companies sort things out between themselves. At Swisscom you can find support here:
Tel. 0800 800 800
or
Private customers: Contact via hotline, chat, message | Swisscom
Here you may only have to request that the case be escalated to 2nd level support, who should sort this out together with BMW if necessary.