How do I put a space between numbers without the keyboard switching to ABC?

Using the onscreen keyboard on the iPhone or iPad I often need to write a telephone number. I like to separate the area code from the rest of the number, and also write out phone numbers as XXX XXXX, with a space in the middle--but if I hit Space, the keyboard changes to ABC and I have to tap again to change back to 123 (Numbers) to finish the phone number--not a world shaking problem but a nuisance when you have to do it over and over. Is there a fix for this?---an example of something that is supposed to make your work easier, working against you. Thanks.