Congratulations!!
There are a few other differences between Charcoal (Anery B) and Anery A than you mentioned. Anery As tend to be more contrasty, while Charcoals are more muted. The difference is more apparent at birth. There is so much variety within the Anery morphs that sometimes as a snake grows it can be hard to tell the difference. Anery As have more of a tendency to develop browns or peaches if the snake is male, while Charcols tend to stay more monochromatic. Charcoals can develop yellow sometimes, but I think the quality of yellow is a little different. Charcoals typically have coal black eyes, but I think that's something that can vary as well. As more Charcoals are being bred sometimes their eyes are a bit lighter.
Looking at pictures of as many different examples can help, but the differences are pretty subtle.
Really the only way to know for sure sometimes is to look at the parent's genes and also do test breedings with your snake. Do you know what the parents were? Where did you get your snake? If you got it from a breeder and they labeled it as a Charcoal there's probably a good reason for it. If you purchased your snake at a pet store or something then perhaps it's less certain.
It's kind of hard to tell from your picture, but I wouldn't totally discount that snake as perhaps being a Charcoal.