Poor customer service

I had initially booked a standard flight with the airline in May , however lockdown happened and our tickets were made vouchers. I booked a new flight minutes after I receive correspondence of my 14h00 flight confirmation, just after I receive correspondence of the time changed to 16h00 no explanation. I contacted thier consultants with no luck and in the next morning consultant takes thier ****** time to solve my problem to change this flight. I've heard people complain about the poor service and client service. This is not acceptable