Costa Rica Again 15

So here's the deal, Gentle Reader  Since I don't have a valid credit card other than Visa Debit for online purchases, my travel agents at Flight Centre refuse to change my flight for me.  The flight will be on Friday, March 20, Air Canada, leaving San José, Costa Rica for Toronto.  i have to pay a difference of $941,90.  The only option is that someone phone them in advance, then come down to their store, 1051 Davie Street, and they will open for someone to pay on my behalf, cash or debit.  I will repay you in full upon my return to Vancouver, plus, you get a free drawing of mine (your pick)

Here's the phone number 778) 783-4972 Otherwise, if I wait till my scheduled departure April 2, and there is no guarantee that flight will be available.  I am truly stuck and am really relying here on your good will,Gentle Reader.  Many thanks