There are several, including Callcentric and
VOIP.ms, who have happy users on this forum.
I agree that Anveo's plan is hard to understand. I may be able to help you with that.
https://www.anveo.com/business/service.asp are the choices for the outgoing line. If you choose the "Free" plan and you are in the US, it is $0.80 per line for 911 and $0.01 per minute for calls out to the US.
Then for incoming calls, you pick one of these:
https://www.anveo.com/business/mainphonenumbers.asp Regular Caller ID is included, but $0.009 per incoming call that is not in your phonebook for name lookup.
For number porting, see
https://www.anveo.com/faq.asp?code=faq_did_portin In the US, that would be one-time $15 per number, or free if you pre-pay for 'Office Unlimited' rate plan for a year.
I have a feeling that the church usage is fairly light but with bursts of use, so you might do well with Anveo Value=free + Starter=$1/month +$0.80 for 911 totalling $1.80 monthly on each line plus usage. Then just pay for the minutes at roughly a penny per minute. The first 40 minutes in on each line would be free. Pay the $15 each to port the 3 numbers. These presume you are in the US. Canada would be cheaper.
Forget the references to FAX in the descriptions. That would be if Anveo was going to handle the FAX rather than you using your own fax machine.
Caveat: I am just a light residential user, so I may well have mis-described something.