Zendesk Inc, the software company under activist shareholder pressure to abandon its $3.9 billion all-stock acquisition of the parent of online survey portal SurveyMonkey,said on Thursday it had rejected an acquisition offer from a consortium of private equity firms for as much $16 billion.

The offer from the private equity firms, which Zendesk did not identify, was in the range of $127 to $132 per share in cash, the San Francisco-based company said. Zendesk shares jumped 10.7% on Thursday to close at $114.18.

The company is facing calls from activist investors, including hedge fund Jana Partners LLC, to abandon its proposed acquisition of SurveyMonkey parent Momentive Global Inc, which it agreed in October.

Read more: Reuters