Hi there happy to help.
Press and hold the Power and volume buttons.(I know you have tried this)
Next........Release ONLY the Power button, keep holding the volume.
Now a menu should appear giving you the options to Fastbook, Recovery, Clear Storage, and Simlock. Select Clear Storage. Use the Volume Down button to navigate the menu.
Press and release the Power button once more.
Wait for your device to reboot.
Let me know,
I tried that and I do not get a menu it still keeps flashing samsung
How old is the phone?
over a year old
Has it gotten wet or physically damaged in any way?
It's my daughter's phone, as far as I know it hasn't. Her battery wasn't holding a charge so we took out the old battery and put in a new one and it just flashes samsung
OK, the phone has a hardware issue. Please call here........
The phone has a 1 year warranty however ask them what they will do for you, as you are just out of warranty.
At the least they will offer you a repair or refurbished replacement at a small fee.
Let me know how it goes.