PSO chief executive Gillian Bremner said it received a letter from DHB chairman Joe Butterfield responding to its request on Friday afternoon.
''I understand your client's disappointment in not being selected the third provider for home and community-based services, but the DHB is not revisiting that decision. Accordingly, I can not agree to a meeting to discuss reconsideration of the selection process,'' Mr Butterfield said in the letter.
PSO's board would meet on Thursday to decide whether to go ahead with legal action against the DHB - which could mean going to court.
She could not say which way the board was leaning at this point.
''Obviously, it's a significant issue and it wouldn't be a decision that's made lightly,'' she said.
However, she was confident in the legal opinion supplied by Dr Royden Somerville QC, which identified flaws in the process that led to the decision to dump PSO.
Southern District Health Board chief executive Carole Heatly said in a statement it was sticking by its decision to drop PSO.
''We believe we have been through a fair and transparent tender process and that we have appointed the best possible providers to care for those who require home help in our community.
''The process was externally audited and the new model of care, which will provide an enhanced and more flexible service to clients, extensively consulted on and supported,'' Ms Heatly said.
A petition calling for the board to reconsider closed at 5pm yesterday and Mrs Bremner expected the final tally of signatures to number more than 10,000.
