You need approval from your general and XS for a number of reasons.
Requesting the name change over the website is okay and should be done by youself, just don't go and change your xbox gamertag without approval.
- To make sure the gamertag is not in use in another division, or is not too similar to another members name (unless they are okay with it - some members that are good friends may purposely have similar names)
- To make sure the gamertag has not been a user that has made the DNR list or is not welcome in the community anymore
- Check if the name has been previously used by a different member in the past (although I have seen this done so not 100% sure on that policy)
This is done to avoid confusion and also prevent you from being mistaken for somebody else (especially in situations where that member has made the DNR list).
This is why when requesting a new gamertag, you are advised to give at least 3 options, just in case one fits the above criteria and is void.
Note: You do not need permission to make a general name change (i.e if I wanted to change my name from La Poison Ivy to Harley Quinn - BUT you do need to advise your clan just so they know), you only need approval for KoG, XGC, SYN or XGG gamertags (i.e La Poison Ivy to XGG Poison Ivy).