A LR or Performance model 3 can absolutely, positively charge at 48amps, given the correct charging infrastructure. "Right charging infrastructure" = Device capable of passing through 48amps, and appropriate breaker / cabling.
With that being said, there are very few instances where the difference between someone charging at 40amps on a 50amp breaker and 48 amps on a 60 amp breaker will make any impactful difference at all in a persons ownership / charging experience.
I get wanting "the fastest it can go" (I really do, I did that too back when I got my model 3 performance in 2018). Given that this OP is charging at 40amps on a 40amp breaker, I wouldnt pay anything to change it, though.
Here is teslas estimation of charging speed. The difference in 40amp vs 48amp is 37mph to 44 MPH. The number of times that 7 additional miles per hour is going to make some difference in the OPs charging experience is likely "almost never" or "never".