Service Provider Router to Access Point or Personal Router

I have a wireless (WISP) internet service provider and their antenna mounted modem (their terms) acts as a router as it will assign IP address to my wireless and wired device when I plug in my wireless access point. I matched their IP address range (10.10.216.xxx) when I setup my access point and other equipment (range extender and additional access points) but now they remotely changed their IP address (10.10.213.1) on the modem and I can no longer access my devices in my network via the IP address I had assign in the original subnet (10.10.216.xxx). I do not have admin access to their equipment. I originally matched their IP address subnet as I have been told not to connect routers in series as it is bad practice but I believe it may be my only option. If I use a router (DHCP enabled) with a different IP subnet (192.168.1.1) after their modem is this bad thing? Or is it okay as long as both routers are in different subnets?

Thanks,