No coverage at Lake Roosevelt, Washington

I have been going to Lake Roosevelt in Washington State for years now. For the life of me I don’t understand why myself and hundreds of Verizon customers cannot get service on the lake. My friends who have AT&T get 4G LTE all over the lake. There are several towers out there, why is it that Verizon doesn’t have an agreement to use those towers?? I have been a loyal customer since 2006, I personally do not want to switch to AT&T. Can someone please look into this? If I were to ever have an emergency on the lake, having no service would delay any help I or anyone that is a Verizon customer would need.