There were reports at the time that Chancellor Jeremy Hunt stepped in to urge HMRC to reverse its decision.
Mr Harra said ministers were aware of the plan to close the helpline, and the date it would be announced.
But he added that “ministers conveyed their concerns about the strength of reaction”.
Now the U-turn had come, Mr Harra said he was discussing funding for more call centre staff with ministers.
However, he said that digital-first strategy was still in place, but that it would be introduced more slowly than planned.
“We are not knocked off our strategy, but knocked off its implementation course,” he said.
Mr Harra said more people were being drawn into paying tax, known as fiscal drag, and that was a significant reason for more people contacting HMRC.
He also said people’s tax affairs were becoming more complicated.
