You can use a disposable number to get a verification code from the chosen service. After that the number will be archived and non-valid for reuse.
Also, you can purchase numbers to receive SMS from web-services permanently. You can find these numbers after registration in your personal account in the “Choose number” – “SMS numbers” section.
Make sure that the chosen number has a “for registration” label! Numbers without such labels most likely will not receive verification codes.