My iPhone 6 won't hold a charge

Sounds like you battery is defective. Download the app Battery Life and test it or better yet, take it to an Apple Store for evaluation. Testing is free, replacement will depend on warranty status and location.

But won't this reset & delete everything from my phone?

My I-Phone 6 has the same problem AT&T is of no help.

I’m having a similar issue, I’m fed up with apple and all their products. They were great for a period but the quality has gone down hill drastically. Time for Samsung.

Go to Settings > Battery And Check your Battery Usage which Apps Consume more power.

Try Doing a Reset

Go to Settings > General > Reset > Reset All Settings

If Reset Won't Fix your Issue Check your Battery Health by Running Apple Self diagnosis test by Requesting from Apple

No Apple Store near me and I have done a reset