Is it illegal for WeChat to swear? Can you call the police?

Illegal, yes. According to Article 42 of the Law on Public Security Administration Punishment, whoever repeatedly sends obscene, insulting, threatening or other information and interferes with the normal life of others shall be detained for not more than five days or fined not more than 500 yuan. Wechat swearing infringes on the reputation and personal dignity of others, which involves breaking the law and can call the police.