You're now nyquest-limited to sending fewer symbols per second (baud), but you might be able to use a larger "vocabulary" of symbols.
This was one of the big changes in modem design. The first 300 baud modems used one 1 bit/symbol, but the V34 modems used a bigger symbol set that could send 6-10 bits/symbol (and also sent the symbols faster).
You're now nyquest-limited to sending fewer symbols per second (baud), but you might be able to use a larger "vocabulary" of symbols.
This was one of the big changes in modem design. The first 300 baud modems used one 1 bit/symbol, but the V34 modems used a bigger symbol set that could send 6-10 bits/symbol (and also sent the symbols faster).