The total amount of mobile data is every mb you're using.You obviously don't know what "max speed" means. It's the fastest speed the cell tower can deliver every given second. Meaning,if you're in an area with many users,the speed goes down. This normally happens in the evening when people starts watching movies and TV and uses their phones as hot spots.You'll almost never reach the official "Max speed". This is how it works and nothing to argue about.
You did say 5GB/month. We're talking about the total amount of data you're using/month, and I know for sure the speed you're paying for is not very fast.
You are lucky because YouTube isn't very picky when it comes to speed. It just automatically lowers the resolution. A consistent 2Mbps works fine, but you can never watch anything streamed. I can watch everything,TV-shows and movies on my Android box,but I need at least a consistent 7-8Mbps to avoid buffering,but my speed is normally way faster.
5GB per month? That's like 2,5 day for me. My limit at NT is 200GB/month.You can't use your phone very much. According to my phone, I'm using about 140GB/month.
I'm on a 6 months subscription max speed no limit with NT for 619 baht.It should have expired June 30,but it's still alive. I have expected it to die every day in July,but no. Go figure. 👍