Last month the Nigerian government announced it had reached a peace deal with militant Islamic group Boko Haram.
The extremists kidnapped the girls from their classrooms in April and although some have managed to escape most have not been heard from since.
Videos have been released in the past showing the girls being forced to convert to Islam.
But on 17 October Nigeria's army announced a ceasefire had been reached which would see the girls released.
Chief of defence staff, Alex Badeh, said: "They've assured us they have the girls and they will release them... I am cautiously optimistic."
Boko Haram has now put a video statement online saying this is not true.
Leader Abubakar Shekau said: "We have not made ceasefire with anyone. We did not negotiate with anyone. It's a lie.
"We will not negotiate. What is our business with negotiation? Allah said we should not."
He said all the girls had now converted to Islam and had married other Muslims.
Shekau said they were living in their married homes and would not be returning to their families.
It's unclear where or when the video was recorded or whether it is authentic.
Revd Canon Hassan Jon from the Anglican Diocese of Jos told Premier it was still unclear if any deal had ever been reached.
He said Boko Haram had so many factions that agreeing a ceasefire with just one part of the group would not be enough.
"After all while Nigerians are losing hope that these girls are either intact or they will eventually be released," he said.
He added: "We don't know how Boko Haram will have kept them all together. Where will they be? How widespread are those girls?"