poor service not paying back

I have taken out a package form Rain who offers a 5g router for R1000 a month. They advertised that if you cancel in the first month you get your money back.

I had the product for a week and returned it to them.

I have requested my cash back and haven't received it. its been 3 weeks already please can you assist as they said it takes only two days from the day the product is collected.

I sent them mails and tried to call, was on hold for 30min and no assistance. They also don't reply on the mail I have sent.