I am afraid you were advised incorrectly and unless you have the email advising you of this or a record of the phonecard then you probably won't get anywhere.

If you do and this advice came before you booked if you complain to Marriott you may get somewhere but realistically it's highly doubtful, from my experience Marriott takes ages to consider anything and generally does not a lot.

I am just thankful I have an ambassador who is a star as anytime I have dealt with the non ambassador agents in last 6 months it's been painful and generally I have had to correct them on what the terms of various things are in the program!