I think someone might be using my wifi

Hi,

I hope I tagged this right.

I called Charter yesterday and they showed me how to access my router and see what devices are attached to it.

I saw an (unknown) device and I asked them how I can remove it. They told me I could not, but if I changed the password and name of the network everything would be ok.

I looked up the MAC address and saw that it was to Liteon Technology Corporation. But it is from China.

I changed my password and network name. So last night I did not find it on my router. I connected my laptop, xbox, and phone. They all showed up just fine but this morning I saw the same MAC address.

I feel like it is someone,but I could be paranoid.

What else can I do?