How to use as WIFI only by switching SIM Card off on MR1100

I would like to be able to use my Netgear MR1100 occasionally as a WIFI router only by switching off my SIM card to be able to connect by Wifi to another Wifi router on my astrophotography setup.

Is this possible please?

Is it simply some "switch" in the setup please?

Any help gratefully received

Thanks in advance

Len