A short while ago, I scheduled a guild match for my guild at 8:00 AM. However, when I opened the game again, I found that a friendly match had been added instead of a guild match. I am certain that I did not add any friendly match and that I scheduled a guild match, not a friendly one. I hope this issue can be resolved.

No it can't be.
It's an happening bug from time to time.
Like I answered you: I can remove the friendly game, nothing more.

I’ve been playing in VF for about a year, and for the first time something strange happened to me: a friendly match was added instead of a union match. What’s even stranger is that the team I faced in the friendly — which has been inactive for two months — made player substitutions during the match, which is an unprecedented incident.

Link match
#match?mid=6307921&summary

Preset changes during the game is a VIP option, not an incident.