sachinsehdev Hi
Try add the specific css rule-set In JA Builder as illustrated in the blog documentation
.header .jub-block .shape-round.btn{text-decoration: none !important;}
how to make a phone call when button is pressed on the mobile device
You can wrap the text around href like this :
<a href="callto:+0400111180">Call Rimple 0400111180</a>