Hi! Nalin
With my experience us embassy will not call the sponsor(they didn't call mine) US Embassy just need an address and telephone number of a person in usa, that will be your contact address once you enter usa. USCIS office will send your Original Green Card+SSN and other documents to this address. That is why they specifically mentioned address and telephone should be correct.
Note- If we are changing the point of entry(POE),we could change our address and telephone number upon arriving in usa-at immigration office.
We were thinking that us government need to know that we have some body in usa to support us at the initial stage, some thought us embassy need to know how much of money we have in our savings. Actually to see us government does not look for those so strictly.
Infact we have won the dvlottery,its a us government program and they will grant the visa without any hesitation, only thing is they need the original documents what is required at the visa interview to verify.
I don't know about the embassies in other countries, how they will treat the dv lottery winners. There could be some differences in certain countries depends.
But our colombo us embassy is so good, they don't put any one in trouble, long as our case is approved from us visa center(KCC) and all the documents are in place.
Good luck