Phone always says I don't have enough storage

First - Your Sim card is only to contacts storage.

Second - You should check your internal phone storage and then add a Micro SD card to upgrade that storage capacity, Anyways there’s some phones that we can’t transfer the apps to the removable storage(Micro Sd) but you could try. Settings - Apps - Click on the app - Move to SD Card.

This is the best i can do with your infos. You should consider upgrade your phone,remember to always check the internal storage should be at least 32Gb.

When your storage is insuficient, it may be caused by the following factors:

1. You downloaded and installed apps and kept saving the cache. The Android phone stored all these data so that the storage becomes less and less.

1. Your favorite content, such as music, movies and images, occupied the Android phone storage.

# If you do not clear the old messages and chats in Android phone, it is also possible to cause the phone says you do not have enough storage.

And you did the right thing to clear the caches. There are many things you can do:

Tip 1: Add a Micro SD card to upgrade the storage capacity.

Tip 2: Manage the media content.

Tip 3:Delete useless files and messages.

Tip 4: factory reset the phone. But you should first backup the data.

Yet, of course, you can buy a totally new mobile phone if you have enough money.

You can check more details here.