Can a pledge be absolved because of mekach ta'ut

My friend approaches me to ask support for a new synagogue. I visit the new synagogue and see that it is a synagogue in the tradition Sepharadi Aram Soba. I make a pledge of $1,200, to be sent in $100 each month.

After a few months, I happen to visit the synagogue. It is no longer a Sepharadi synagogue at all. It is now a Breslov chasidic synagogue.

I call my friend and ask him, what happened to the Sepharadi synagogue you asked me to support? He answers me that it started out Sepharadi but the committee voted to change it to Breslov.

Am I obligated to continue paying the balance of the pledge. Or is this a case of mekach ta’ut, in that the synagogue changed the condition under which I originally made my pledge?

Mekach Taut! You can stop sending money.
But since you pledged that money to tzedaka, find another place to send it.