1:7 not that there is another one, but there are some who trouble you and want to distort the gospel of Christ
The Holy Bible: English Standard Version. 2001 (Ga 1:7). Wheaton: Standard Bible Society.
Paul stresses the importance of guarding and protecting the pure integrity of the Gospel. It should not be added to or taken away from. The language Paul uses or ‘not there there is another one’ suggests the emphasis of existence. Paul is emphasizing that there is only one Gospel and none others exists.
The reality is that there were some who distorted the Gospel of Christ (note the possessive tense). Paul’s emphasis on one Gospel written by one Author draws a line in the sand of firm establishment that no other variation of the Gospel will be even be considered. In this historical context the issues of circumcision and observance of holy days had been established as an additive to the Gospel, which Paul quickly resisted.