When my phone storage is ful why

There is no phone that has unlimited storage. You have a limited storage space on your iPhone. You did not mention which iPhone you have or how much space capacity it has. When you reach that capacity, your storage gets full.

Storage space can be quickly filled by Videos, Photos and Audio files. To create space you will have to begin deleting some of those files.

If you have more details on the storage issue then please provide. Thanks.

Axel F.