This issue has been fixed and will be included in the next version (>3.3.0) of the plugin Osclass payments pro, but for anyone that doesn't want to wait, create a file called shopclass.css at oc-content/plugins/payment_pro/styles/ with the following content
.opt_payment, .opt_payment_pro_pack {
position: relative;
display: block;
padding: 10px 15px;
margin-bottom: -1px;
background-color: #ffffff;
border: 1px solid #ffffff;
border-width: 1px 0;
border-radius: 0;
}
.opt_payment a:before, .opt_payment_pro_pack a:before {
display: inline-block;
font: normal normal normal 14px/1 FontAwesome;
font-size: inherit;
text-rendering: auto;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
content: '\0000a0\f03a\0000a0';
}
.opt_payment a:before {
content: '\0000a0\f03a\0000a0';
}
.opt_payment_pro_pack a:before {
content: '\0000a0\f09d\0000a0';
}