Is there limit to make outbound call from a phone number

Hi folks!

We were sharing one default phone number with all of our customers to give an experience of our product but while sending more than INVITE SIP message using SoftPhone TS (https://github.com/ringcentral/ringcentral-softphone-ts) to make an outbound call to multiple phone numbers, we’re receiving OK response for only 5 of them, not receiving anything at all for other requests.

Is it something we can fix or is it RingCentral system limitation ?