You can go to survey look and feel to change same, 

Refer this page for same

https://www.qualtrics.com/support/survey-platform/survey-module/look-feel/general-look-feel-settings/#ChangingNextAndBackButtonText

I’ve been using the Look & Feel section to adjust the arrows in my troubleshooting, but I’ve been unsuccessful. For example, I tried to simplify to > and < but it still looks strange. See screengrab. 

I’ve tried deleting everything in the Next and Back button boxes to see if that would only display one arrow, but that didn’t work either. See other screengrab.

Have you applied and published if you are testing with live link? 

If it doesn't work can you check by clearing cache or with other browser

I have clicked Apply each time. I haven’t published the survey yet because we are still making edits. 

I ended up adding in Next and Previous to the boxes and that seems to be working when I do a survey preview.

Thanks!

You can try html code for ">" and <

Entity numbers look like this: &#entity_number; To display a less than sign (<) we must write: &lt; or &#60; Entity names are easier to remember than entity numbers.

I think you may be using the new survey taking experience (previously simple layout).

Perhaps you can try inserting a space?