Paying off halifax mortgage issues

V2001

I was given a redemption letter to pay off mortgage. I started making payments via online banking over 4 days to pay the total off. I phoned to check balance before I made last final payment and the advisor said he would cancel my direct debit payments to. The letter I had advised against cancelling direct debit.
Now my last final payment hasn't come off and it's 4 days later. Halifax don't seem to have a clue and they not helpful. Who can I speak to or is their a complaint procedure? The last payment was over 19k and should have cleared my balance but it's not even showing its hit my account 

penners324

Have you spoken to Halifax today?
Did the last payment have the correct reference?