There could be many reasons they use both company names.
The company regstered in alibaba is Weiershen, but the domain name says Asia Top, and you can see also Asia Top Technology Co. http://goo.gl/w8OehW
I suggest you to ask directly them about this. You need to check:
1- What company is sending you the quotations?
2- Ask about company account and check the name you will pay.