Call Sign for GA

[FlyStav 0]

I tried hard to find the answer, but i couldn't.
I have an Cessna 172 airplane with tail number, say, G-BGMP (Registered in UK, and i want to fly in UK).
So, when i am communicating with ATC, i want my Call sign be like "Golf Bravo Golf Mike Papa" - just my tail number.
I entered Tail number, but it's required to fill Callsign in config. If i enter "Cessna", my call sign will be "Cessna Golf Mike Papa". 
In User Guide there being said "Valid General Aviation call signs include 3 types" and "a. Full Tail Number: November Three One Victor Bravo". But where is the option?

[Dave-Pilot2ATC 870]

It should recognize Golf Bravo Golf Mike Papa if you put GBGMP in the tail number box and Cessna in the Mfg box.  Be sure not to put in the dash (-).

Dave

[FlyStav 0]

8 hours ago, Dave-Pilot2ATC said:

It should recognize Golf Bravo Golf Mike Papa if you put GBGMP in the tail number box and Cessna in the Mfg box.  Be sure not to put in the dash (-).

Dave

It's a magic.
Yesterday i tried to speak "Golf Bravo Golf Mike Papa radio check" all night. I tried all possible accents. Controller was not answering me.
I even tried to do that via "Say it" function, but no luck.
So, i wrote this post.
Today i read your message.
I tried again.
...
"Golf Hotel Alpha Bravo Sierra You are loud and clear."
!!!
How can it be? )))
Thank you, sir )