Two whites were jailed this week and a third charged after engaging in rare acts of civil disobedience to protest the South African government's policy of banning critics of apartheid.

Jacqueline Bosman and Ilona Kleinschmidt entered prison yesterday to serve sentences of four and three months for refusing to answer police questions about their visit to a banned friend, Winnie Mandela, a longtime foe of apartheid.

David Russell, an Anglican priest who is banned, attended the synod of his church in Grahamstown, several hundred miles from his home in Cape Town. Russell's banning order requires him to be in his house each night after 6 p.m. He was charged Monday with violating a banning order, an offense that carries a maximum three-year sentence.

The three protesters are unusual for their willingness to go beyond verbal protest against the government's practice of banning. Although many whites, especially English-speaking, say they disagree with banning, few take direct action to challenge it.

About 150 people, mostly blacks, are presently banned in South Africa, according to the South African Institute of Race Relations.

A banning order is meant to prevent a person from normal social intercourse so that he cannot influence others. Most banning orders prohibit the individual from speaking to more than one person at a time and from attending a "gathering." A banned person's movements are usually confined to the magisterial district in which he lives.

Banning orders are imposed by the minister of justice on the recommendation of the police and cannot be contested in court.They are generally used against people whose political attraction and leadership are noteworthy. Many prisoners released from Robben Island, South Africa's most notorious political prison, are banned in an apparent attempt to stop them from telling others what conditions there are like.

Russell, who was given a standing ovation by white and black churchmen at the synod for his defiance of the banning order, said in a telephone interview, "It was a religious protest. It's a statement of belief that we banned people ought to question the whole matter and should no longer go on being our own jailers without question.

"The whole process of banning is so unjust. The only way to cease being silenced is by taking the kinds of risks to make a statement about what banning means.

"We are normal people, not fanatics who need to be silenced. To silence dissent is one of the most potent prescriptions for violence in any society.

"If enough banned people decided, 'enough,' I think we could start making a powerful statement," said Russell, who ministers to black migrant workers.

Last November, Russell was charged with three counts of violating his ban, imposed in October 1977. His trial on those charges has not been completed.

The priest's action comes at a time when black-white tensions are ripping at the multiracial fabric of established churches. The churches are responding by reassessing their roles in a society that condones legalized discrimination. Part of this reassessment involves a growing official church support for acts of civil disobedience to apartheid.

Bosman, a graphic artist, and Kleinschmidt, a legal secretary, both refused to answer questions from police and a magistrate about their visit to Mandela because their statements could be used in a case against her. They were convicted of contempt of court.

Two other white women who visited Mandela earlier served one month in prison for refusing to answer questions about a visit to her.