all_or_conditions = []

if request.GET.get('filter_phone'):

      all_or_conditions.append("phone='"+request.GET.get('filter_phone')+"'")

if request.GET.get('filter_email'):

      all_or_conditions.append("email='"+request.GET.get('filter_email')+"'")

if request.GET.get('filter_whatsapp'):

      all_or_conditions.append("whatsapp='"+request.GET.get('filter_whatsapp')+"'")

sql_query = "SELECT * FROM app_table WHERE " + " OR ".join(all_or_conditions)

SELECT * FROM app_table WHERE email='user@email.com'

SELECT * FROM app_table WHERE email='user@email.com' OR whatsapp='15557776655'

phone = request.GET.get('filter_phone')

email = request.GET.get('filter_email')

whatsapp = request.GET.get('filter_whatsapp')

q = Q(pk__in=[])  

# something result-less, not to have an empty query in your disjunction 

# that would hold for all entries

if phone:

    q |= Q(phone=phone)

if email:

    q |= Q(email=email)

if whatsapp:

    q |= Q(whatsapp=whatsapp)

qs = qs.filter(q)