Missed Call Message

[Adept]

So today I missed a call from my dentist and my phone sent a message saying "I can't talk now..." I've had this phone a while and it never done this in the past until I had to wipe the phone so I'm not sure if it reseted some setting or something but it's no use to me and I'd like to know how I can turn this off. 

[Thommo]

It's not supposed to reject with a message unless at the bottom under the answer slider you tap reject with message

[Uliwooly]

Settings > call settings > answering machine 

[Adept]

Yeah it was sitting in my locker in work so it's not like I "Rejected" the call. It just sent out a message automatically.