I run a small business and I'm also the guy in charge of IT as well because I have to keep costs low and I'm relatively technically savvy. But this business phone line stuff is so confusing, with terms like PBX box, SIP trunking, etc.

I did some basic searching on this subreddit and the general advice seems to be for small businesses, don't run your own pbx box b/c of complexity etc and go with a provider like https://voip.ms//business/pricing

But it seems crazy expensive. For example, if I use my business line 20 hours a week, that means that its 4,800 minutes a month or $48 a month at VOIP.ms level of pricing. Not to mention the fact that there is a $1 charge monthly just to have the number, and a separate charge (albeit small) for all calls received.

That just seems so much more expensive than a normal consumer cell phone bill that has ONLY voice.

I literally just need a separate business phone number that can work through a CISCO IP phone I bought secondhand for myself and a couple of employees. Is there any way to save on the monthly bill / basically only pay for the phone number itself? I can't imagine this day and age where everything goes over the internet and bandwidth is not charged on a usage based basis (at least in the US) that I need to be paying for IP phone calls "by the minute".

Help me understand if there is any way I can set this up using selfhosted or if I'm really looking to do something that is impossible. Just a complete noob to the business phone industry and the software stack needed to run it.