Here's my situation:

I bought a UA ticket last week (for May) using one of the 5k / $75 e-certs. This week they had a schedule change which resulted in a 3 hour time shift, which doesn't work for me. It would be possible for them to put me on a connecting flight at around the same time, but I don't prefer that option.

Is a 3 hour time shift grounds to cancel the ticket and ask for a refund? (This is what I'd like to do, since there are now better fares available.)

If they agree to cancel the ticket, what happens to the e-cert? Can that be reactivated? Or issued as a travel credit? I don't feel that I should forfeit the e-cert since it's not a promotional hand out; I actually paid for it in miles.

Thanks.