@foreach ($Resellers as $Reseller)
<option
    @if($Reseller_id)
        @if($Reseller->id===$Reseller_id)
            selected
        @endif
    @endif    
value="{{$Reseller->id}}">{{ $Reseller->User->name." [".$Reseller->User->mobile->mobile."]"}}</option>
@endforeach