How do I use the telephones

Hint 1 of 5:

They take credits, so you need some on your credit card.

Hint 2 of 5:

Click on the card slot and it will be inserted.

Hint 3 of 5:

You must know what number you want.

Hint 4 of 5:

Click the *known* numbers and then click upper right key to enter.

Hint 5 of 5:

When done, click on slot again to get back card.