A person who—
(a)sends, by means of a public telecommunication service, a message or other matter that is grossly offensive or of an indecent, obscene or menacing character ; or
(b)for the purpose of causing annoyance, inconvenience or needless anxiety to another, sends by those means a message that he knows to be false or persistently makes use for that purpose of public telecommunication services;
shall be guilty of an offence and liable, on summary conviction, to a fine not exceeding £50.