Friends who know how to communicate can help solve it. Now I have a hotel. The front desk phone is connected to the room phone, and the room phone can be dialed outside.

Yes, I wonder what equipment you are using now. But let me tell you clearly that your request can be realized. A number opens multiple channels. General IAD, you can set up five extensions to talk at the same time. If you want more, you need the operator to open it. Actually, in your case, it depends on how many rooms you have. Generally speaking, it is enough to open three numbers, then one IAD, one number is the switchboard, and the other numbers are extensions and hotlines.