Are you saying that you installed a Tesla Walll Connector? If that is what you are using, the problem is that the electrician did not set the amperage correctly in the Wall Connector (the same thing happened to me). Take a look at the manual for the wall connector. There is a little dial inside it that specifies what the amperage is of the circuit you are using. It defaults to “1” which is 15A (of which 80% is usable, hence the 12A). You need to set it to 30A which will give you 24A of charging, or double what you get now. You can do this yourself if you’d like (I did).
If you want to do so, first of all make sure that you shut off the circuit breaker to the Wall Connector.
Then, you need to remove the outer case of the Wall Connector. This requires a Torx security screwdriver (read the manual to see which size you need ... I think it was a “20”). Once inside, just use a small flat-head screwdriver to change the setting.
Or you could just ask your electrician to come back and adjust it.