Poor Internet service provider

What an excuse of an Internet service provider. I have a 100mb download and upload package. Now being in IT myself, I know speed doesn't matter. Latency matters. My twitter videos buffer, Facebook switches to mobile data, my games lag all the time. I've logged tickets with them before and the only thing they say is that the line is testing perfectly. How's about check your DNS resolution time. Check more things. I even got myself a gaming router thinking that things will improve. Well it hasn't. I ping my local network devices and there's no issues. As soon as I ping Google, or Twitter, or EA.com I get massive response times and packet loss. Now I'm paying R1330 a month for broken service and I can't switch to any other ISP coz they have a contract with this complex I live in. Fix your issues please.