Ordered a samsung S8 plus last month on the day of...

Ordered a samsung S8 plus last month on the day of arrival i emailed them asking if my phone had even been shipped and then, then they told me they didnt have the right colour of phone in so i picked another one they told me they would either post it that day or the nect few days a week went by i still had no phone. So i asked for a refund they said i would have it within 10-14 working days them days soon came along still no refund so i emailed them and they said in the next 3 working days so should of gone in on friday 6 july 2018 oh and iv still not had my 499.99 refund im fuming and something needs to be done about it and if i dont have my refund then i may have to take it further anx get perfesional advice because its a lot of money to be losing out on! Until i have had my refund this will stay on!