Cox Mobile is simply an MVNO. Mobile Virtual Network Operator, running on Verizon's towers. Cox purchases deprioritized cell tower capacity in bulk from Verizon. So Cox Mobile customers compete with Verizon customers for access to the cell towers. Verizon customers always get priority. So if there are a ton of people connected to one tower trying to use data or call/text all at once, then Cox Mobile and other MVNO's are severely throttled so that Verizon customers continue to get a relatively good experience. Cox Mobile doesn't have its own cellular infrastructure, but instead leases access to Verizon's network to offer its mobile plans. Google is the same, all their Pixel devices are also MVNO's but do a better job at handoff and management of data between the Carrier and Wi-Fi.
