Struggling with slow uploads

I have been experiencing bad upload speeds well below my purchased plans for months now. The problems began when a tech realized an animal had chewed through our incoming line. Unfortunately, after the service was restored, our upload speeds remain well below where they should be. After two separate attempts with service techs coming and giving up on the problem, I upgraded our package in the hopes of better speeds. It worked for a couple of weeks, but now we are once again about half of where we should be on upload speeds. Download speeds, incidentally, are BETTER than our plan's published speeds. We have the 300/30 business plan now, and we get about 320 Mb down, but only about 17 Mb up.

However, our upload speeds are FAR less consistent. They will typically bounce around between 4 Mbps and 17 Mbps. Typically, we will see them hover between 10 and 15. I'd like to get to the bottom of the problem, since we're paying for speeds we cannot achieve. Thank you!