How can I restore my phone without an update?

Hello

my iPhone 8 Plus is disable and message me: iPhone is disable, connect to itunes.

I turn off the phone and go to the recovery mode, ask me to do an update first and then restore it.

my net speed is not good and it takes about 2 hours to download 3.2 GB new ios update.

But unfortunately after a few minutes the phone goes out of recovery mode and returns to the screen giving the same message => Iphone is Disable. connect to itunes.

How can I restore my phone without an update?

I can't download update because my net speed is very low.

Please help me