Gate against telegram bot. How to protect yourself?

Question

Information Security

The gates to the holiday village are opened by a call to the service number. A malicious defaulter uses a telegram bot to make a call with a substitution of the number. It turns out that there is a call from the administrator to the service number. There are logs, there are camera recordings.
How to fight?

Answer 1

I don't understand what answers you expect.
The obvious one is to implement a more secure authentication and authorization method that cannot be bypassed by a simple telegram bot.
Legal hooligan - put a brick on the hood, coat the car door with shit + piss, threaten with a court, sue.

Answer 2

Require the input of some password by tone dialing, for example.

Answer 3

after a call from the client to the service number - immediately reset and call back. If they picked up the phone, open the gate; if they didn't pick it up, don't open it.
Well, or another option for the caller to send SMS with a code that he must send to another number. Compare code match