A lot of phones now a days have features that enable data use if a wifi connection is low quality, (which would help with slow or buffering internet connection). You can turn them off in the settings, called "Wifi-Assist". You can alternatively just ...
@Eliza5 You could try to reset the connections, which would clear the cache for internet passwords, mobile service, everything that involves networking. If after that and it doesn't work, could also try removing the sim card while the phone is powere...
