Why am i playing for pure fiber when the service isn't being delivered?

[wireless]

I spent the better part of 2 and a half hours on the phone last night with customer service. Initially for my "940 download/940 upload plan I've been speed testing around 200 download 100 upload. So after being on the phone for a long time, somehow he got it to 500 for each. I was okay with that. This morning, it's back down to 268/113. how can they justify charging these rates to customers without having to fulfill their end of the service with little to no repercussions. I'm getting fed up with this and from the forum, i am far from being just a one off scenario. Does anyone have any ideas what i can do to remedy this on my own? I don't want to waste more hours on hold unless i have to.

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