There are some dialing rules built into Teams that cannot be circumvented:
- Numbers beginning with ‘0’ are converted to full E164 numbers. If you have extension numbers beginning with ‘0’ then consider changing them so they don’t have this prefix
- Many PBXs have feature codes beginning with ‘*’ that can be dialed. Most will work from Teams, but *11, *12 and *13 do not. Microsoft have indicated that they reserve the right to block some other two-digit star codes as they allocate them for new native Teams features, although at the time of writing there is no sign of this. If you make use of these blocked feature codes then look to see if the PBX can be configured to change the codes to ones that will not be blocked by Teams.
- You may have a number of public short codes for public services. Perhaps these are being handled as internal extensions rather than PSTN calls. Perhaps you are dialling bespoke numbers that do not translate as expected. Again, the issue here is that Microsoft expects everything to be dialled in the E164 format and treats anything 6 digits or less, in length, as an internal extension.
Please see this Microsoft article: Create & Manage Dial Plans