4/5 Days of my stay, hotel did not change my bedsheets. On the morning of 4th day, I went down to the reception to request them to change the bedsheets because it was dirty.
Reception said they will do so, when I got back at night and checked, the bedsheets were not changed. There were two distinctive indicators that I used throughout my stay to identify whether the bedsheets were changed.
1) black marks on the top right of the bed
2) small hole in the bedsheets
Thankfully the bedsheets were changed when I requested them to do so again