This is confusing!
You say you booked the ticket on your blue card. That means that you paid for the ticket at that price with that card.
You cannot change the form of payment because the charge has already been made. The only thing you can do is cancel the ticket and get a refund after a few days. You can then book it at the current rate on the card of your choosing.
You state that your father had miles. This means that you wanted to cancel and use miles to buy an award ticket. That is a totally different cost factor all together. You either pay in full with miles and use a card for the fees or you pay partially with miles and partially with a credit card.
In any case you do NOT have a reason to complain. It is your responsibility to make sure you know the t&c of what you are trying to do. As is the case with this posting, you did not make it clear your intentions or what happened. I highly suspect that is the same scenario with your conversation with the agent.
Try rinse and repeat, but complaining will only set you up for future blacklisting.
YMMV