I'm using Vonage Business (was Vocalocity), it's like $20/month/extension. Phone numbers were no extra charge.

What I did is many of my phones are set to the same extension, so I don't get charged for them.

I'm using Panasonic KX-TGP550 phones which, while simple, are extremely reliable. They've been running for years with no issues.

I've gotta remember to call them and delete my fax line, it's been over a year since I last got a non-spam fax and probably more than a year before that for the previous non-spam fax.