Glad you got it "working", if you think that it calling repeatedly is "working".
For me, I need a system that connects 100% of the time, reliably, with my central station. Most central stations will not accept VoIP unless it's done their way (if they have one). Google Voice is not reliable for this type of usage.
If my alarm goes off, I want the alarm company notified, immediately, without error. I don't want them saying "oh, that's the guy where his system calls us repeatedly, and it's never been an issue".
I went from POTS service to Google Voice and implemented an internet device that the alarm company provided, which was supposed to tell them every X minutes that the communication device was working properly, and supposed to accurately transmit to them information. I had it for about 15 months, went through 2 iterations of the device and a replacement to the second. I eventually learned, by discovering issues, that this type of monitoring wasn't reliable and they'd be having issues all along, many unknown to them at the time. Only my persistence in getting the solution reliable exposed these issues and resulted in my returning the device to them and switching to cellular. While it costs more ($12 more per month), it's reliable. It's also battery powered from the system, so even in a power outage it works for a period of time.
If your internet goes down, you have no alarm notification. Nor does your provider know you're offline unless the regular daily/weekly/monthly (most are monthly) test doesn't come through. So if you have a fire during an internet outage, they get no alert.
I added this as I don't want people to think that GV is reliable as an alternative to a POTS line for alarm monitoring by a central station. It is not. It's great that you have it working, but be careful.