Security Gate Problem calling iPhone XR

We live in a gated community with a Verizon call box that lists a 3-digit code for each resident. Dialing the 3-digit call initiates a phone call to the resident's linked phone (either cell or land). When the phone rings, the resident answers and presses "9" to open the gate.

My code is linked to my iPhone XR. My problem is that when my code is dialed from the call box, the call goes DIRECTLY to my voice mail so I never get the call and therefore cannot open the gate for the visitor.

The gate phone number is in my contacts list; it is not blocked. I have actually made an outgoing call to the call box so my iPhone would "recognize" that number. Nothing works.

I did not have this problem with my iPhone X.

Any suggestions? Please do not suggest I contact an App developer. This is not an "app." It is a service of my residential project.