Why is staff at Oyster card help line so useless?. You call them,
explain your problem/issue and they say "I will get back to you
shortly". A few days later you call back and can never speak to the
same person ("he/she is not available. I'll get him/her to call you
back").

Wait few days, and you call again ......

Also, why do they always insisting that you FAX your issue/problem to
them?. Someone should teach them how to use e-mail.

I woudn't bother with the "help" line. Use the email option in the "ask
oyster" section of the TfL website. Emails seem to get dealt with much more
quickly and the people who answer seem to have a clue what is going on.