Making a phone call in iOS

I've been trying to make iPhones dial any kind of phone number, I'm stripping the variables down until it's just this tel://9897816789 And then I call Application.OpenURL(PhoneNumber); the string above with the tel:// is exactly what is put in PhoneNumber, it works fine in android even without stripping out all spaces, parenthesis, and dashes but I can't get tel:// or telprompt:// to work on an iOS device. Anything I find that uses swift or iOS normally without unity refers to functions and classes we don't have in unity and seemingly have no equivalent to. I'd rather not make a native plugin because I think that would be a huge performance hit every time a button that calls a number is called. There has to be some way for this to work in unity, it works perfectly and easily on android, but unless there's some function or formatting I'm missing with my string PhoneNumber variable I can't figure it out.