How to make an iphone call without it showing up on the bill?

My husband gets our iphone bill and I don't want him to see some calls I'm making for his birthday. Gonna surprise him with some old friends coming to visit and tickets to a concert and I don't want him to see weird numbers on there and be like… Huh? Lol

Is there a way?

Oh please everyone knows you are really cheating on him and don't want him to find out its okay! This is the internet you are anonymous! You don't have to make up birthday stories!

To be fair… Captain sushi makes sense (sorry). But if hes right then thats wrong!
Answer- you can't so i think payphone or new temporary sim card that your iphone accepts. Or you could download watsapp or touch or something and see if these people also have it (you would be surprised so many ppl have watsapp cuz its free on android n cheap on iphone touch is free on iphone) and try and message them atleast then there's no numbers cause its all through internet ;-)