Can’t Sign up without Japanese Phone Number?

I am trying to register an account at [piccoma.com](https://piccoma.com), but it gives my (American) cell phone number the following error:

**Landlines and**
**phone numbers beginning with 020 or 050**
**cannot be used.**

Well, my cellphone is not a landline, and doesn’t begin with 020 or 050, but, I guess it doesn’t like American phone numbers.

Is it possible to create a Japanese phone number with Google or something? Any help is appreciated!