problems with very noisy office

I have a problem with our phones. We are a small startup and we bought (originally) yealink T21PE2 phones. While they work well, we have a very noisy office environment (very noisy, since it is a small office) and the sales people have a hard time making calls. All of them use YHS32 headsets and those don’t help at all.
We are looking for a solution to get better headsets that offer noise cancellation (eliminate background noises) and I was hoping you have suggestions for us. wireless would be nice but I don’t care if it is wired.
In emergencies I am open to upgrade the phones as well but that would be an extreme solution.

thanks

claus

p.s. ooma offers the yealink yhs33, are those any better ?