Call lag

For a long time now my wife and have experienced what I think is termed lagging which results in the first part of our speech not being heard by the other party in the call. This is very annoying as we are required to keep repeating the first part of our speech. For example if we give our post code as OX4, the person at the other end does not hear the first letter “O”. 
I engaged in a long chat with Smarty and was told a maintenance issue was receiving attention in my area. That was months ago and the problem is still there. Anyone else having this issue?