Hi Andres,
Indeed, font for that element as I saw was defined by template styles. Default style looks like that:
.sp-page-title .sp-page-title-heading {
color: #fff;
text-align: center;
font-family: Cormorant;
font-size: 136px;
font-style: normal;
font-weight: 400; }
.sp-page-title .sp-page-title-sub-heading {
color: #fff;
text-align: center;
font-family: Nunito;
font-size: 24px;
font-style: normal;
font-weight: 400;}
Create Custom CSS and override font name and etc.
In your case probably you need only that line:
.sp-page-title .sp-page-title-sub-heading,
.sp-page-title .sp-page-title-sub-heading {font-family: Helvetica; }
Simple, right