The original GSM Logo was created by the GSM MoU Group Marketing Planning. It is not used any more since several years:

The Group Marketing Planning also chose GSM as the system name.  This is described in an article of Yngve Zetterström.

The group developed a ‘Corporate Identity Guide’ which ‘has been designed as a work of reference, with the aim of making the GSM corporate image a uniform one’ (quote from introduction.  It describes the format, the characters, the colors of the logo and how to use it on phones or SIM cards.