Disable mobile data for sim card

[jaclaz]

@Neph

/ip dhcp-client
add interface=*4

Here you have an issue, see point #21 :

GP & CSA for Mikrotik devices

Preamble and disclaimer: The following is a numbered list of what is usually considered good practice or common sense advice when choosing, using, setting up or maintaining a Mikrotik router. It is my personal take on the matter, and in no way approved, endorsed or recommended, officially or unofficially, by Mikrotik or their partners or by anyone else. In other words you are perfectly free to ignore its contents, though they represent (IMHO) a sort of (useful) check list for people starting …

You want the device itself or traffic through the device (or both) to be blocked?

Rules could be like:
/ip firewall filter
add action=drop chain=forward in-interface-list=LAN out-interface-list=WAN
add action=drop chain=output out-interface-list=WAN

but no idea if the second would block also SMS sending, maybe you need to insert an accept rule for the port(s) used.