6b1 error and call disconnect when apartment entry system calls my cell

[DougRaven]

My apartment entry system calls my cell when someone tries to buzz my suite.  I receive the call but immediately after answering it, the call disconnects.  The guest hears the message “6b1 The number you have reached is not in service”.  We switched the entry system to call another PM number with the same result.  We switched it to a cell with another provider and it worked fine

[DougRaven]

We’ve tried an iPhone 12 and iPhone 15.  Both have been on PM for a year and everything works fine with them.  The apartment mgmt said to try switching to another carrier. I called the entry system company and they said their system just makes a regular phone call - nothing special.  Also tried having a “1” in front of the 10 digit phone number but that didn’t change anything.  As soon as we changed the entry system to call a number on another carrier, the call could be answered and pressing 9 unlocked the door as expected. 

[hTideGnow]

hi @DougRaven 

what phone do you have?

you just cannot receive calls from the Apartment entry system?or people call you and got the same 6B1 error?

Try Reboot phone and Reset network settings