Replying to all of this to say that the artist and I talked about all of the issues. I raised the concern of the quality of the artwork along with the full body vs knee issue. What happened was that they did not see it as necessary to make the piece more polished because my character "did not have as much detail" as other characters they had drawn for commissions. I get where the knee reference may have implied that the piece should be knee instead of full body, however, when I raised this point, the artist gave me the excuse that their "default" is a knee and that an upgrade to a full body was free. I was not made aware of this and was pretty upset because I had scoured their entire website and saw no mention of this.
As of Monday, this was all resolved. The artist finished my piece to the standard of the examples on their website and offered a partial refund.
I'm not sure where to put the rest of the conversation for you all to read so I attached it in this comment!