Complaint Review: National Awards Commission

I received a notification some weeks ago to say that I had been awarded ?600,000 and for a fee of ?12.89 for handling, a cheque would be released to me.
As with all this type of junk mail, I put all the paper back into the return envelope and sent it back WITHOUT A STAMP or payment (I'm not that stupid).
Today I got another piece of junk mail from the same company saying that it would seem that a mistake had been made, and that they had not received my ?12.89, and as a result, my request is in jeopardy and has been placed in a state of "LIMBO".
The latter is not signed, but purports to be from a Ruth Collins, Deputy Director, Office of Oversight Payment Committee.
Do they never give up??

John
Airdrie
United Kingdom