I think you have 2 options.
1/ stay on the 1 plan until you want or need to upgrade your phone. As long as you stay put you will have unlimited tethering
2/ change plan, I recently did this, and do a bit of hunting on Android forums ( assuming you don’t get an I phone )
Guy in the store was quite helpful about sidestepping tethering limits in so much as he did say it was doable, pointed me at searching forums but didn’t actually show me how, but did hint he had set his phone up and it was easy.
As yet my tethering hasn’t been close to the 2 gig limit so I haven’t bothered
My plan is unlimited data hence 2 gig tether, lower data plans have lower or NO thither limits