Ecom Express — supporting fraud companies like simply shirt store

I have ordered 3 nos. Xxl size denim shirts with simply shirts store online, but they sent cheap quality useless shirts through ecom express.
When i tried to contact them they are not disclosing any contact no. And simply sending mails that they are looking into it.

After that i got doubt and checked online and to my surprise, there are n number of complaints about this company "simply shirts store.

My concern here is that how come a company like ecom express supports such a fraud company like simply shirts store and collects money on their behalf. I request the ecom express to share that companies contact address so that i can proceed legally on simply shirts store.

Thanking you.