I would take advice rather than reading the guesses here.
Very common actually - people trading or practising under shortened versions of their names
you know like Ralph Fiennes instead of Ralph Twistleton Wykeham Fiennes - I mean those Harry Potter films would have finished before you had completed prounouncing his name
and I dont really think you have to do much about it
( but if you have shortened Moshoeshoe to Mo then you cant point to Mo's signature ( yours) and say o that is not me )
The money laundering regs interfere
and you can imagine somewhere like the TSB looking at the mistake - and saying 'oh yes this is very very bad - we will have to do nothing for up to six months!'
My father had one document Peter Paul Pedant as Paul Peter Pedant - o my god didnt the civil servants scribble !
and that was 1936. [ oh no problem joining up and fighting for King George in 1939 ]
Pity his name wasnt John John Pedant .....