Why is Straight Talk saying ive used up all my high speed internet when I put airtime on it yesterday?

If the plan you have offers high speed data for 30 days and you use it up before that 30 day period, you then wait until your 30 reset, for more high speed data, whether you have paid for more or not.

Get your paperwork out and re-read it. Or better yet, call customer service and have them explain the high speed details of the plan you have. 

In all seriousness not joking at all walmart Straight Talk is terrible as a serious source of a phone service or hot spot service.  They're scammers.  And have been sued for being scammers.

Because Straight Talk is literal sewage.

EVERY cell phone company reserves the right to throttle your usage if you are a bandwidth hog.

There is a finite limit to cell phone capacity so they WILL throttle the largest users or even terminate them if they repeatedly exceed their agreed to plan limits.

Buy yourself a real phone and service. Stop wasting your time with gimmicks.