I phone 7 Storage

[Rodders]

Hi all,  how do I clear the Storage category 'Other' in my phone. It's pretty much disbaled my phone, as I can do barely anything without it saying 'no storage' 

It currently shows as over 20GB of my 32 capacity even after after cleared out anything I dont need.

I've gone down to the bare bones in terms of apps etc. 

Have tried various solutions that have been suggesting online but nothing moves. 

Any suggestyions greatly received.

Thanks 

[MI5]

@Rodders 

I find the best way is to back up with iTunes then factory reset the phone.

Once you reload the back up it seems to have removed a load of the junk.