Airlines move flights. Most of the time it is by twenty minutes and nobody notices; occasionally it is by a day, or the flight disappears from the schedule altogether, and what you do in the first few hours makes a real difference to how it ends.
A schedule change is not a delay
The first thing to understand is that a schedule change is not the same as a disruption on the day. A change notified weeks ahead is a contractual matter between you and the airline, and airlines generally have a published threshold — a number of hours of difference — beyond which they will move you to an alternative without charging you, or refund you. Below that threshold, they usually will not. That threshold is the airline's, it varies, and it is the single most useful thing to establish before you start negotiating.
The second is that your options are usually wider than the one you are offered. When an airline reaccommodates you automatically, it puts you on whatever its system found first, which is not necessarily the flight you would have chosen from what is available. If the automatic option does not work for you, say so promptly and ask what else is open on the same terms. Being early matters here more than being forceful: the alternatives get taken.
The third is the part people miss. If a change makes the trip pointless rather than merely inconvenient — a connection that no longer connects, an arrival after the event you were flying for — that is worth stating explicitly rather than accepting a seat on a later flight because it was offered. The remedies available for a schedule change and for a cancellation often differ, and so do the remedies where a connecting itinerary was sold as one ticket rather than two. Whether your booking is one ticket or two is worth knowing before anything goes wrong.
If you booked with us
If you booked with us, this is what the agency is for. Open the booking under My Trips, or call the desk; we will look at what the airline is actually offering rather than what its app is offering, and where we hold the ticket we can act on it directly. As a General Sales Agent for Mahan Air, that is particularly true on Iran routes. On any airline we can at least tell you where you stand, in plain terms, which is usually the thing that is hardest to get at short notice.
Two habits worth keeping
Two practical habits. Keep your contact details current on the booking, because a schedule change notice that goes to an old number is a schedule change you find out about at the airport. And check your itinerary a week out even if nobody has contacted you — notifications fail more often than schedules do.