Applies to: Call2Teams
If when entering phone numbers against user the error The telephone number provided is not valid is received:
Then this is because the number should be in e164 format to be mapped to MS Teams, please try adding a +1 to the front e.g. +1205
On the user setting the number must always be in E164 format as this is a constraint of mapping to MS Teams which needs a number@domain user identity.