Back in 1992, I booked a 7 nt Bermuda cruise for mid- September. Got a call a couple weeks before sailing and asked if I'd be willing to go a different date? Rebooked for 2 weeks later, got a full refund, only paid port charges for the new booking.
In 2017, I booked 2 OV on a 16 nt TA. Got a call a couple weeks before sailing asking if I would be willing to switch the 2 OV cabins for 1 2BR GS. Took them up on the offer. And no, we didn't get an extra point for the suite.