New domain, log-in problem

I had a URL under the hosts name, now i have proper domain name but you can acsess the site through both URLs, now im asking here as my hosts arent helping me and i want my site to work soooo….

basically, when i log into the new URL .com/wp-admin i log in but it takes me to my old URL .ord/wp-admin then i log into that and i takes me back to the .com and then back to .org so neither will let me in… its constant.

My host said to make sure the URLS are both pointing the the new Domian name in PHPmyadmin but i can see how or where to do it…

im soooo confused and want to work on my site…

thanks.