It will mean he is set to miss the clash with Real Madrid.
The RFEF code says insulting a referee comes with at least a two game ban.
Mateo Lahoz sent off Dembele for saying "very bad, you're very bad" after he dismissed Ronald Araujo on the defender's Barca debut.
In 2016 Celta midfielder Fabian Orellana was banned for three games for telling the referee "how bad you are". Two for the insult and one for getting two bookings.