<div class="hemen-ara">
        <a href="tel:telno">
            <span class="fab fa-whatsapp"></span> Hemen Ara
        </a>
    </div>

.hemen-ara {
    width: 90%;
    margin: 0 auto;
    height: 65px;
    line-height: 65px;
    text-align: center;
    color: #fff;
    background: #25D366;
    border-radius: 65px;
    -webkit-border-radius: 65px;
    -moz-border-radius: 65px;
    display: block;
    position: fixed;
    bottom: 50px;
    left: 0;
    right: 0;
    font-size: 4vmin;
    z-index: 99999;
  }

  .hemen-ara a {
    color: #fff;
    display: block;
  }