May I get my deposit back from a photographer (services contract) when we haven't signed a contract?

I would say that it depends on the terms of your contract, but since you don't have one . . .

You don't say how much you gave as a deposit, but here are my suggestions:

Send them a letter (return receipt requested so you can prove they got it), canceling your request for their services and requesting the deposit back in full.

They can choose to honor your request and refund your money. They may not, however and here's why: When you booked them and reserved their services, they blocked out time for you and your wedding. Presumably, you booked them well in advance to guarantee they would be available for your wedding date. They can't be in two places at once, so they may have had to turn down other jobs on the same date.

You may be able to get a refund from them if they can book another job to fill the spot you've kept reserved for the past 5 months. If they do book another client, then you may be in a better position to ask for a refund, since they really didn't do anything substantial and they didn't lose any work. They may offer a partial refund if the job is a smaller one or if they have done anything substantial toward fulfilling your contract. If they cannot or do not book anyone else for that day, you may lose your deposit, since they lost not only your work, but other jobs for that date as well.

Good luck and congratulations on your upcoming wedding.