Add this code to the Custom CSS field on the Style tab of your Click to Call widget’s settings:
[class*="Main__Component-sc"] {
right: 50% !important;
transform: translate(50%, 0) !important;
}
.eapp-click-to-call-window-show,
.eapp-click-to-call-window-component {
right: 50% !important;
transform: translate(50%, calc(-100% - 4px)) !important;
}