I love FreePBX and yes, Sangoma bought them, but the SIP Station pricing has never been “reasonable pricing” IMO.
For most people with simple usage, I recommend VoIP.ms, Twilio, or Skyetel.
SipStation only offers a flat rate per “line” offering of $22.99 per month. Any service charging a flat rate per “line” is costing you too much money.
There are 20 working days in June of 2019. That equates to 160 working hours assuming an 8 hour work day. That equals 9,600 working minutes in June.
$22.99 / 9,600 = $0.0024 per minute just to have that single call path available.
The OP wants more than 3 lines available. Let’s assume 5.
This brings the cost to $114.95 per month. That is a relative $0.012 per minute.
But that per minute rate is assuming that you are on all 5 lines for 8 hours a day for 20 days. That means you are on the phone for 48,000 minutes in the month.
That is not reality. More likely, people are on the phone a fraction of that. So buying service on a pay as you go solution is much more cost effective.
Let’s start with the $114.95 assume cost for 5 “lines”.
If you go with a pay as you go service, you will pay something less than $0.01 per minute most of the time, but that is a nice round number to work with. Also, you have no restriction on the number of “lines” you have. If 10 people call at once, it will ring. Assuming you have your FreePBX instance setup to handle that.
At $0.01 per minute you can be on the phone for 11,495 minutes. That is a lot of minutes in a month. I have systems with 100+ extensions and barely hitting 10,000 minutes in a month, but they consistently have 8-10 lines in use multiple times per day.
Conversely I have a system with 20 extensions hitting 20,000 minutes a month averaging 5-8 lines in use at once during the day.
Determining what SIP carrier to use is a math function and nothing else. In that context it is almost never (yeah for exceptions) logical to purchase flat rate SIP trunks.