What do I need to do to return an unwanted item???

I am APPALLED by the service of One Day Only - I ordered a helmet on the 8th of June 2020, requested a return the day after because I realized that I ordered the wrong size.. till TODAY, the 28th of JULY 2020, no one has assisted me.

I was told that my package would be collected between 8 am and 5 pm on Friday the 17th of July 2020 and nothing, till today, still nothing.

I have sent many emails requesting an exchange and to date, only been contacted twice but nothing was ever followed up.

I am disgusted, I understand waiting between 24 and 48 hours for assistance, it has been longer than a month and this is pathetic