How do I remove a theme's button styling?

I am using a theme to style my form but I don't like the picture that is used for the submit button. How do I remove this aspect of the theme?

I've tried uploading a new image to replace it but that didn't work.

I checked your forms and it appears that none of the forms have the submit button that is the same as the screenshot you have provided. Here's a screenshot of the submit button seen in your form.

Can you please provide a URL of the form in question so we can further assist you? We will wait for your reply. Regards.

 

Yes we ended up customising it manually
...

If you have applied a custom theme that has a lot of customization, it is quite hard to edit it, we can use custom CSS code to tamper the existing design of it. But if you have a lot of customization, I recommend applying the default theme and use the Form Designer Tool to fully design your form. 

If you need further help on this, please do let us know.