Gst registration and tax

my client have business of flat-co
nstruction. he obtained Gst registration numbers in 2017 and remain in 12% gst slab. now his scheme is over Now he wants to start new scheme in same name and same gst registration. nearby his old scheam. my question is he can continue his old gst registration for new scheam. old rate was 12% but from 1/4/19 gst rate change 1% or 5% so my question is that he can continue his old gst registration or new registration. properitor is same.