Phones have no IMEI
 

I have purchased some dual sim mobile phones from China. When I inserted sim cards, all the phones registered 'invalid sim'. I tried to retrieve their IMEI numbers and discovered that the IMEI numbers consist just of zeros, and I do not think that this should be a valid IMEI. Is there any way that I can generate IMEI numbers for these phones, as I think that the problem lies with the lack of IMEI. Thanks.