So my messages usage is 800 MB , how can I remove all data from my phone? there is no "clear cache" option
so after searching for a while , I found a solution for my question. i was be able to delete the entire 717 MB from my phone and from the icloud backup without jailbreak.
the solution is by deleting the imessage hidden cache from the itunes backup the restore ur iphone from this backup . here is how:
1- backup ur phone to itunes,
2- download and run a program called iBackupBot ( it allows u to explore itunes backup on ur computer).
3- while inside the program go to : iphone > system files > Mediadomain > Library > SMS > attachment ..... the folders inside the attachment folder are the pictures u have sent and recieved . so delete all of them.
4- go to itunes and restore ur iphone . "restore backup...".
5- after restoring ur phone, go to icloud and delete the iphone back up and make a new back up. this will remove the imessage cache from icloud too.