10DLC Brand registration won't accept support number

I'm trying to submit a 10DLC Brand registration in Pinpoint SMS, but it keeps being rejected because the Support Phone Number is invalid. The field shows "+1 555-0100" which isn't even a valid phone number in the first place (no area code) and it isn't accepted anyway. I've also tried the formats:

• +1 (555) 555-5555
• +1 555-555-5555
• 1-555-555-5555
• 555-555-5555
• (555) 555-5555
• 5555555555

But none of them are accepted. What do I need to enter here?