You can opt out of your property appearing on portals that are aimed at students or tenants with pets or tenants on DSS but you may still receive calls from prospective tenants who don't meet these criteria. This is because the advert appears on the major lettings portals and anyone can look there. This is all part of the vetting process but to limit unsuitable enquiries state on your advert if there are any applicants that you won't be accepting (be aware; you cannot state anything that would fall foul of the Discrimination Act).