My text message keeps getting rejected because the phone is saying I should use the area code.

I made a phone call and didn't use the area code when I dialed the phone number. My phone allowed the call to go through, however when I try to text the phone number it I get an error message saying "invalid number of digits/use 10 digits." So I added the area code and I keep getting the message. I saved the number in my contacts with the area code and I keep getting the same message. Also the person can text me but I can't respond because the phone keeps saying I'm not using 10 digits. Help????