We recently migrated to Microsoft Teams with hosted Direct Routing for PSTN connectivity. We have 5-digit extensions configured on the PABX. Those extensions are non-continuous with range from 20000 to 60000 and around 830 of such extensions are in use. We would like to get a 1000 DDI number block and do 1:1 mapping so that Teams users can reach the PABX extensions. Something like this: Teams Dial Plan (5-digit extension to DDI number mapping) -> DDI number goes to PSTN network -> on-premises PABX -> Reverse DDI to 5-digit extension mapping. Now the challenge is, given 50 normalization rules per Teams Tenant Dial Plan limitation, 1:1 mapping using Dial Plan is out of question. 5-Digit extn to DDI mapping can't be done using RegEx because the extensions are all over the place and 1000 number block won't be enough to build the RegEx logic. What are our options? (Note: We are using Direct Routing in hosted SBC model. Hosting provider is not in a position to implement translation on the SBCs)
