signal messages pictures files and other contents are stored locally on your device. these contents are readable by the open source signal clients. because everything in signal is end to end encrypted the signal service does not have access to any of this data. you can permanently disable your phone number from being recognized as a signal user by unregistering your phone number here. you will need access to this phone number to verify and complete this action.
you can delete your content from this service.
combined quote text and tldr
You can delete your content from this service
{'signal.org'}