When my brother got married 2 years ago the bakery sent the wrong cake...not the wrong flavor cake, a completely wrong cake, different design then what the bride and groom picked out... she ordered a round 4 tier cake they sent a square 3 tier cake, she ordered ribbons and swiss dots, she got damask print which was sweating like crazy and was smeared all down the side of the cake....weird!
And strangely enough the wrong cake's colors did match her wedding so no one knew any different BUT she came right to me and said...Make sure you take pictures!!! So I documented the whole thing, even the inside when it was cut which again strangely enough was the correct flavor...hmmm.....so when she called the bakery the next day to let them know she had all her back up ready to go.
She wasn't a Bridezilla and everyone enjoyed the cake and no one knew any different but us, she just wanted to let the bakery know that it wasn't correct and she was smart enough to take pictures!!!!!
I know if it was me and I knew I was going to call the bakery to let them know it wasn't the correct cake I would document everything w/ pictures and even save a piece or two to show the baker! How can she dispute a filling flavor that you don't even have available???
I hope you everything turns out in the end for you! I'm sure someone there has to have a picture or something to let you know if they did get the correct filling. I'm just a true believer if you're going to complain about something you better have proof to back it up!