Gotta say, at this point I'm quite interested in what is correct concerning tower ownership.
Lazy marketing by the wireless carriers in general has made the public think that towers are something more than tall metal structures capable of holding antennas and radios, but that's all they are (don't get me started on CSpire's ads about putting more towers in Davis Wade or Vaught Hemingway....they may have added more antennas but ANTENNAS ARE NOT TOWERS). Any given tower can generally hold several wireless carriers at different heights but it's up to each carrier to design their network as they best see fit. Most cell towers nowadays are owned by one of three big tower companies, Crown Castle, American Tower, and SBA, with a number of mid-sized tower companies out there and a few mom-and-pops. Most of these companies will build a tower to suit one or more carriers that's interested in locating in a particular location and hope to lease out space later to others. It's generally pretty rare for a wireless company to build and own their own towers anymore, because that means you have to also be in the real estate and leasing business, and most of them would prefer to not do that. CSpire had held on to a lot of theirs for a long time, outsourcing the management of them for several years, but recently even they have started to sell off some of their towers to a tower company.
That's way more information than you wanted to know, but you asked.
As to the original statement about CSpire coverage north of Panola County, I don't work for CSpire, but I'm familiar with their spectrum holdings, and they've sold or traded away of a lot of spectrum in Desoto, Tate, Tunica, and Marshall counties in the past couple of years, and what they have left is higher-frequency and doesn't cover terribly well. In the old days (20 years ago), they didn't have a network north of Panola and Lafayette Counties, and it costs a lot of money to build and operate and upgrade a wireless network, and I can only assume their market share north of there was not such that it justified deep investment going forward. They've done the same in most of Alabama and northwest Florida as well; they've mostly consolidated their spectrum to their traditional service area of the lower 78 counties of MS. It's probably cheaper to them to roam on somebody else and devote their network investments in places where they have a stronger foothold.