Teams Calling and Voice mail issue

Hello Members, From last week we are facing really weird issue with MS Teams calling. When our users are dialing any domestic mobile numbers it is ringing but some reason if the mobile users are unable to answer the calls then the Teams user unable to leave the voice message. the other weird issue is during the dialing process the mobile user will see the call drops and then reconnect and this is happing 3 times then the call is disconnecting. on the Teams user side he will only get an error message "Sorry, We couldn't connect you". This error is only coming if the mobile user is not answering the call. Domestic landline numbers as well as international mobile and landline numbers are working fine without any issue. if anyone faced this issue and got the resolution then please need your help.