Provisioning number using Twilio IncomingNumbers API

I'm POSTing the following url:

https://api.twilio.com/2010-04-01/Accounts/AC8a2..../IncomingPhoneNumbers?PhoneNumber=+13103417563

And getting the following error with no error number

400 is not a valid numbe开发者_Go百科r ]]>

Anyone know why this is happening?

The plus in the phone number translates to a space, usually. You should try omitting it or then encode it.