Connection issues as former sprint customer switched over to tmobile?

I was a very happy sprint customer-happy with bill, happy with connection, happy with customer service and very happy with my old phone.   AND THEN…..merge happens and I have to purchase new phone, because of the merge and the latest/greatest 5g.  So I purchsed new phone...(after unsatisfactory service at 2 different tmobile stores) and was told my new service with tmobile was actually $15 cheaper than my sprint service and I was getting a great buy-back of my old phone.  So...after said “great” deal...now paying $30 a month more,  and after less than happy customer service-I am now having connection difficulties, which I never had before.  Text messages and photos dropping off,  no service in some locales….WTH????