Garmin VivoSmart HR+ quality and refund issue

I bought a Garmin VivoSmart HR+ fitness Smart watch from OneDayOnly on the the 30th of January 2018. I was very happy with the product until I realized in September 2018 that the strap is coming off on the one side. I contacted OnedayOnly and they arranged to collect the product for assessment. Early October they contacted me back saying that I will receive a full refund for the product. I then requested to rather have the item replaced as I was happy with the way it worked. They then agreed and sent me a new watch. I was happy with it, until I realized in March 2019, that the strap is coming loose from the body of the watch once again. I then realized that this is a quality issue on those models. I went through the same process again with OneDayOnly and they collected the watch for assessment once again in April 2019. After it was collected they let me know that the supplier has fixed the watch and they will be sending it back to me shortly. I then let them know that I am not interested in receiving it back, because it is clearly a quality issue and I am convinced the same will happen again. Also, I do not understand why they were not able to fix it the first time round and pushed to refund it, while the second time round they could fix it super quick and return it to me. When I notified OneDayOnly that I prefer to receive a refund this time, they said it was not possible, but that I must just let them know if it gives the same problems again and they will collect it for assessment. This made me furious, because every time I need to send this watch back to them, I have nothing to train with for about a month, no distance tracking, no speed tracking, no HR information, no running history and it is simply impossible for me to train without this information. I have basically paid R2 808.00 for an item that I do not have the use of at all times as it needs to go back to the supplier every couple of months. I would love to get refunded so I can move on and buy a watch that I will have free use of.