LTE data slow on iPhone 8 Plus

My LTE data speed has been under 128 kbps constantly. I contacted my carrier and they said there is no problem with the sim card. I tried all the methods the internet suggested: Resetting network settings, turning airplane mode on and off for a few minutes, resetting statistics on cellular data. It's being so slow, what do I do?

Note: I did get my sim replaced and the issue still persists

Note 2: It started being slow when i updated to 14.0.1. Could this be a problem too?