Hey Howdy Hey Chloe and welcome to planDisney!
Thank you so much for your question about moving the dates of your trip as this can be tricky depending on how far into the future you would like to make these changes. The good news is, you should be able to do all of this yourself and you have plenty of time to do so.
Availability for 2023 will be really limited at this time as Disney has not released package information for 2023 yet which is why you are not able to make the changes to your trip. Disney usually releases this information in early summer, around May or June. After this release, you should be able to make these changes from your
My Disney Experience account which sounds like you have already tried to do.
After the release of the 2023 dates, if you did need assistance making these changes you can
call Disney and a Cast Member will be able to help you through this process.
I hope this information was helpful and you are able to make the changes you need. If you do have any further questions please let us know, we are happy to help!
Have a Magical Day,
Nick