TWG, 

here some suggestions to get into your phone's recovery mode, I hope one of them will work, because of its Samsung software:

Your phone must be powered off before starting!

1.

Try holding the volume up and the home button,

2.

or volume up and down buttons.

Whilst doing so, press the power button for 2-3 seconds, release but maintain the press on the volume button.

If you get into Recovery Mode, use the volume down button to select Wipe Data and press  the power button to confirm. Use the volume button again to select the final confirmation.

3.

All at the same time press and hold the volume up, home and power button.

When the phone boots, you hopefully will be in Recovery Mode. Use the volume buttons to scroll down to reset and the power button to select the option.

Then scroll down using the volume button again to select Yes – delete all my data to confirm the factory reset.

4. 

At the same time press and hold the Power/Lock for 10 to 15 seconds until the screen flashes on.

Use the Volume Down button to scroll and the Volume Up button to select Recovery.

Press the Volume Up button and Volume Down button together at this screen.

Use the Volume Down button to scroll down and the Power button to select Factory Reset, press the power key to confirm.

Use the Volume Down button to select Yes – delete all user data – and press the power button or the Volume Up and Down buttons again to confirm.

Hopefully the device will then start performing the Factory Data Reset. Once the formatting is complete, press the Power button to confirm a reboot.

If it works and I hope so, your phone will be as new, like it was when you bought it.

Good luck to you!

Hi Ulrike,

thanks for your hints but unfortunately nothing of this works and the button combinations are nearly impossible to press due to the wheel design of the Serenata:

Okay 😕  :)

Is there a Sim card inserted?

In any case, power off your phone and remove the SIM card if there is one.
Insert an active SIM card (need to know the pin code) from a different carrier and power your phone back on. 
Now try to type on keyboard *2767*3855# 

Maybe, maybe it will work?

If it does not, I would try to contact Samsung customer service:

Yes, there's always an old signed out SIM card placed in my Serenata as it wouldn't start without one. 

I've found this solution, too but there's NO way to enter "*" and "#". You only get a dial with numbers and "Enter". 🙁

*2767*3855#

Forgotten:

There should be an option to insert this code by typing on the keyboard under "Emergency Call"

Hope it works ...

Just had a look at the manual ...

It's not possible when locked?

Thank you Ulrike for your effort!

This is everything you'll see: 


Login to view image

Lessons learned:
- Ensure to use an identical lock code on identical devices
- Write down every code for every device

😳

As there is shown on the display:

"Sim-Sperre"

I REALLY would insert another Sim card with pin code known!

Guess it will work then.