Sunwing payment plans

Hi, I have a quick question. I booked a trip with Sunwing for me and my friend using their payment plan (deposit now, pay the rest later).
The issue is that my final payment is due on the 18th, but I don’t get paid until the 21st. I called Sunwing to ask for an extension, and they told me to call closer to the due date since they’ll be able to see if there’s still enough time before the trip.
While I was on the phone, one agent mentioned that they often give extensions, but another one said she couldn’t guarantee anything.
So I just wanted to ask—has anyone here requested an extension with Sunwing and actually gotten one? And was it a hassle?
I’m a student, and I can afford the trip, I just need a few extra days to pay once my paycheck comes in.