They planned visit to South Africa came along because they failed to get the visa before the date of departure.

Here's a corrected version of the sentence: "Their planned visit to South Africa fell through because they failed to obtain visas before the departure date." Explanation: - "Came along" is not the correct phrase to use in this context. "Fell through" is a better choice, as it means that the plan did not happen as intended. - "Get the visa" should be changed to "obtain visas," as multiple visas are likely required for a trip to South Africa. - The phrase "before the date of departure" should be rephrased as "before the departure date" for smoother flow and clarity.