I guess you have all your administrative access turned off. I hope you cannot edit registry or edit any powershell commands as well.
But if you can do one of the following, then it will be only your way out.
a) Put this command in a batch file, and run the batch file. If you can run this successfully, then you should do a reboot and the new settings will take effect.
rundll32 user32.dll,ChangeDisplaySettingsA 1280,1024,55
b) You can use other third party utilities like ResSwitch (search the internet and you will find the download link), which lets you run some commands and change the resolutions.
Hope this helps.