Thats causing your problem in GTA online. High speed internet for online multiplayer should be minimum 10 down and 1 up with less than 100 ping. Are you using wired internet or wifi? If you are using wifi what brand and model is the wifi transceiver in your pc? Also things like vpns can slow things down.
I just double checked and im unbanned from online. I get little lag issues even with my much worse setup, there so its definitely your internet messing things up. I get 50-100down (a little inconsistent)and only 6 up with 23 ping Over wifi with my phone. My pc has a cheap usb wifi dongle so its a little slower there, about 50-100down and 5up with higher ping, but does online fine.