Would &#x27;rejecting&#x27; the call result in the calling user&#x27;s operator billing <i>them</i>, though? This is a major concern with international usage, given phone providers&#x27; tendency to... overcharge for what&#x27;s technically VoIP usage.<p>The classical text message verification schemes barely have this issue in most of the world as the <i>recipient</i> pays nothing, but of course the sender gets billed instead.