Good day,
I can assist you with this issue. If you have already changed cpanel password and other credentials and this is happening again and again, then, seems you have a code injection, will need to check the code and/or database of your website to find it and eliminate it, plus hardening the website in order to avoid this form happening again.
Feel free to contact me to share more details and fix this asap.
I've plenty experience in this field since i worked for 18 years as tech support level 3 into a web hosting company.
Best reagrds,
Oziel V.