Slow Internet

I had my internet since last year December 2019. At first it looked like a good deal since it gave me 10 gig day and 10 gig night surfer and paying for the internet month to month. Doing what was required from the internet I experienced the required speed. Recently the internet became very slow and the speed dropped to 2G. Since I also use night surfer I don't get any satisfaction to do stream. Even my B315 router which falls under the 4G LTE Category, and even the area where I reside I do have coverage. I do not mind to pay, since I was a customer for years can cancel this service any time because my internet speed is not getting any better.