The Call filter app doesn't work on a Unlocked S21 ultra. Do not come in here with the usual corporate PR response of we can't guarantee a unlocked device works with all branded features. The phone is the exact same as that sold in your store there's zero difference besides it not being bought from Verizon.
This app needs to work on all devices there is zero reason it doesn't. Everyother carrier has a spam call app that works on unlocked device. Do I seriously need to go to TMobile or ATT to just prevent spam calls? Literally been a Verizon customer for like 15 years and this is most absurd thing I've come across. I will file an FCC complaint if need be, you're still required to abide by the LTE spectrum rules of supporting unlocked device on your network
