iPhone SE Wi-fi connectivity

My phone is great on Wi-fi around the house. If I go elsewhere and connect to Wi-fi, that's fine too. However, if I am out and try to use 4G network, I cannot access anything online nor can I use 'public Wi-fi' networks.

Furthermore, when I get back home, to re-connect to the home Wi-fi, I have to restart my iPhone.

I am using Vodafone as my network and have Norton 360 VPN on the phone.

Does anyone have any suggestions?