Horrible speeds with 1000mb

I am a new customer and from day one my speeds are up to 29-30 mbs while I am paying for 1000mb. They have sent me a new gateway which hasn’t done a thing. I am very frustrated and xfinity doesn’t seem to care to resolve my issue. I have reset the gateway and done everything they told me to do with no resolution. I believe they are throttling my speeds and it’s very frustrating