I don't trust 100mobiles.com if I am honest, I am basing that conclusion on the fact that there are many complaints
on the internet from people who have ordered, but have not received
I know when you see a deal it is the most tempting thing in the world to take advantage of it right away, but in this case I really do think you should remember that "If it looks too good to be true, it probably is".
Depending on what country you are in, remember that you will almost certainly be hit with a large customs bill which you will have to pay before they will even deliver your phone.
The company is based in India, so unless you are there too, you will be eligible for customs charges. This is the fee you pay for having items sent from one country to another. It is a government charge so not something that can be worked out with the company.
Please also check that it is legal to have these items shipped to your country, different countries have different laws and there is a chance that if it isn't acceptable, it will be seized by customs and destroyed, in which case you won't see your phone or get a refund.
Sorry I can't be more positive but it is best to be safe than sorry. Maybe you could try eBay, there are some great bargains on there.