As many out there has their SBC running in their datacenter and not by an servicepartner or Telco who has the SBC as a service.
For you there is a important new stuff that has come in public preview, and that is the SBA (Survivable Branch Appliance) for direct routing.
You need to talk to your vendor and mostly upgrade your SBC to have this support.
So why should you add on a SBA? If you have an internet outage this can be usefull to remain telephony in Teams.
Microsoft say this in their article about it. "Assume that the customer site--called a branch--temporarily cannot connect to the Microsoft cloud through Direct Routing. However, the intranet inside the branch is still fully functional and users can connect to the Session Border Controller (SBC) that is providing PSTN connectivity."
You can read the whole thing here, and it's important to talk to your vender if it's AudioCodes, Ribbon or any other. Do that before you start working on this.
Have a blast out there. #StaySafe