Claudine,
You don't have to call for your reservation - just go to Dollar.com and enter the codes there. That way you can try out different codes etc. on your own time until you can find the best deals.
I have been unable to get a price better than $249.99/wk with $39.99/extra day from Dollar regardless of the codes I use. In fact, the FVG code gives me NO discount. The KISS codes gets me the $249.99 rate but I was really hoping for the $199.99 or $209.99 rate. We aren't going until March so maybe it will go down by then.
Good luck,