I'm going crazy with Amex Canada...any help would be appreciated...

Some time ago a got a supp card for an employee of mine who was taking care of a bunch of my business.

He no longer works for me and I cancelled that card back in September.

The problem is that transactions still keep showing up on that cancelled card. I have called Amex.... I have yelled at them...... I have begged them....
Please stop all transactions on this card.... it is CANCELLED!!!!!

Yet no matter what I do.... they keep showing up.

Amex says that they are all preauthorized monthly charges and that they are my responsibility to pay. I say.... Fu*k you... this card is cancelled and I have repeatedly requested that NO transactions be put through.

I'm going nuts.

Any suggestions ???

MCM