Is OTHER wrong in the post ? POST : So from the title I do sound like the asshole but let me explain

So my grandma (who I live with) has this friend who we will just call Steph and she has a grandson named 
John. Since Steph owns a plumbing company we called her to ask for repairs (we paid for it in case anyone thinks we we EP’s / EK) and she said sure.

So when she came this morning I was getting my stuff ready to study for an important test worth 30% of my grade in English. I said hi and turned to my desk but then I heard John say hi. I wasn’t expecting him to come and I don’t think my grandma was either. I greeted him and went back to studying and he went to the living room. 

After about ten minutes my grandma tells John go in to my room and a told her I’m studying and I’d rather have no interruptions (keep in mind I had planned all my weekend plans around these 5 hours studying and me and John had never had anything in common as he is still In year six and I’m in year 8) so my grandma tells me to just study later even though I had made plans with my friends for about the time they were going to leave so I say no I’d rather get a decent grade and I thought that was the end of it. After they left and I got back from my plans I was told by my aunt (who was also there) that I’m a horrible friend although I never made plans with John, we don’t go to the same school and never have since he lives 20 miles away and we have next to nothing in common.

So AITA?