Save phone number

I use iTunes 12.3 on PC, I tried to update my payment and get an error that I my phone number must be 7 digits long, but why? code of my country is 380 and my number except this 3digit is 9 digit lengths, why I need to put 7 if it is 9? So I can't save updated payment information without a correct phone number, but validation ask me to put less numbers than I really have.