Need advice from an IT baw re Phone Options for Sales Call Center...

I own a retail brand with a manufacturing building, and I want to set up a call center inside my building. (In essence, I am hiring 2-3 people to call retail shops all day to introduce our product to the store owner, with the idea that the store owner will sell our products on their shelves.) My warehouse is about 13k sq ft, and we have a couple of empty offices where my phone sales crew will be stationed. The building has some old phone lines that run from jacks in the walls (adjacent to workstations) to a server room. The Spectrum guy (I'm in CA) just came in and set up some equipment in the server room, but he said his "tuner" wasn't working and he couldn't connect the phone lines with the proper workstation jacks. He said it was someone else's responsibility anyway (apparently Spectrum doesn't run lines anymore.) This means I need to find someone else (presumably a low voltage person) to come out and run these lines. (I should also note that we don't have an existing phone company or service in this building.)

I don't know anything at all about telephone lines or VOIP. Should I scrap this whole Spectrum shitshow and use VOIP lines instead? (Internet is not an issue here.) Are should I proceed with getting this set up and using Spectrum?

Any thoughts or advice would be greatly appreciated!