I recently switched from AT&T to Verizon. I have 6 phones, 3 iPhone 12 max and 3 Galaxy s21 ultra 5g. On 4g service it is very sluggish on all phones. Speed test from multiple sites and servers. Average 3.4 to 5.6mbps . Tried on all phones. Used to AT&T where I had 20mbps with no issues.