What wifi are you using?
Verizon doesn't control the wifi speed anywhere except off their hotspots. Wifi is a function of the phone and the router where you are. And Verizon doesn't control the operating system of your phone.
Check for system updates for your phone---many brands do them automatically but don't know about yours.
Verizon will throttle your data rate over their network if you are using a LOT of data--like streaming video--are in a high use area, and have already used over about 20GB. But that doesn't affect wifi.