Can't dial extensions

When I call a number and need to dial an extension, none of the solutions work on my Samsung A54 (dial the number directly, hit the star and wait for the comma, etc., etc.). Samsung checked the phone and pronounced it in perfect shape. The only solution seems to be with Xfinity/Verizon. I have a friend who has a Galaxy phone and uses Verizon and has the same problem. What to do?