The first step would be to open the modems internal SCC (System Control Center) and look to see if you are in FAP and if any error conditions are present.
Are the two icons at the top center of the page both green ?
"But you could have read THAT in the original question......."
Actually I did. I was leading up to looking at the error codes and conditions that will tell a "story" of their own:
Its called one step at a time.
While you are at it, define "slow" for us.
Link to saved testmy.net results ?