usmobile interview !

hey so i gave my interview at usm karachi (usmobile) and got selected got the offer letter and everything and it had mentioned the batch starting from 15th but after i acknowledged and sent them the signed copy of the offer letter they haven't responded since then. ive sent them an email and texted the recruiter as well. ive heard they ghost ppl a lot but im worried since i have to make arrangements before joining. what should i do? do they usually do this? should u expect to hear back nd is there a number i could call. pls help