Generally, I will send an email a week later, and then send it again 1 week. If not, I will give up.

It depends on the size of the company. If the company is large, you can find the phone number online. Call and ask. If the company is small and can't find a phone, you can visit at home. These are extreme behaviors, and there is really no way to try them.

Personally, I think it's better to send an email ~ it's similar to what the second floor said, but I suggest you adopt mine in time.