Fongo powers free calling solutions for a number of brands. This forum includes information and tips on all of those offerings. Note that your specific services may vary based on the specific Fongo product that you're using.
If you send me your number and the reason why you need it changed, I'll let you know if we can generate a new one. It's a little tricky at our end to change them, so we'll only do it for security purposes (ie. if someone stole your password, device, etc). I'll be able to do this for you on Tuesday when I return to the office.