S7 active not sending receiving Text messages since April update

Since the March 30/April1 update my Galaxy S7 will only send about 50% of my texy messages and I don't really know how many I am not receiving. I turned off advanced messaging, that was the only help ATT could offer (the stores only care about selling new products not servicing existing ones). I saw that others had the same issue, but saw no remedy. 

Can anyone help?