Phone isn't turning on

I know It'd be better a solution to go to an iPhone repair shop with that.

Before I go I'd like to ask and hear if anyone having the same issue as I do.

My iPhone is not turning on now.

When I wake up in the morning I figured out my phone's off. It happens sometime as the existing Battery having some troubles before.

It wouldn't charge till 100%.

Usually it stops charging on 70-80% on average.

And turns off sometime while it had about 30-40% charge.

So I thought that was the issue.

When I tried to turn in on the screen didn't came up, I was just hearing the sound of the empty charging bip (you know what I mean, that warning sound while your'e phone having 10-20% charge).

Then I connected it to the wall charger.

The display is still blank.

Now I'm hearing the sound of charger connecting continuously/repeatedly.

It was just annoying.

So I turned the phone off.

And till then It's not taking charge neither turn on.

I have changed the battery then (as my friend got a spare battery).

Nothing happening.

Any idea would be appreciated.

Thank You in Advance.