Extension and payment arrangements

I previously was given an extension for my payment to April 28th, but then i was also given a payment arrangement afterwards that says i need to make the first payment by the 26th of April. My check for work has a hold on it that i can't get released, im not sure it'll be released in time for the 26th. I'm wondering if i still have til the 28th? or does the payment arrangement cancel out the extension?