OnStar 4G LTE1 and Wi-Fi Hotspot Troubles

So I purchased the "unlimited data plan" through OnStar for $20/mo. I try streaming music and it keeps cutting out. It's like the service is poor? The WiFi signal that shows on my car/iPhone shows full service. When I turn off WiFi everything works fine. I signed up for this as I am on the road for work and it is nice to be able to open my laptop and respond to a customer if my Verizon service on my iPhone is low.

Anyone else have poor experience with this plan? Is there a way to fix this?