The farmers claim that based on that advice, they delayed selling their shares until Fonterra announced its new share value on May 30.
Many people were surprised when the price dropped from $6.79 to $5.57 despite the milk payout reaching a record $7.90 a kg of milk solids (kg/ms).
Former Southland dairy farmer Greg Roberts sold his 400-cow farm earlier this year and said in an interview the new owner did not want Fonterra shares, leaving him the option of cashing them in at $6.79 or waiting for the new price, announced at the end of May.
He said he asked Fonterra staff for advice and was told the share price had been appreciating and also that December's forecast interim share valuation for the season was $7.01.
In announcing the lower share price, Fonterra chairman Henry van der Heyden said it was the result of higher cost of capital, the rise in commodity prices squeezing retail margins and higher milk prices affecting the value of its core ingredients and global trading business.
In a separate dispute, Mr Roberts said Fonterra has told him he would lose 30c a kg of milk solids from this year's record payout, money directors were considering keeping as retained earnings.
"So that drop has put us back just on $200,000, and then the announcement of retained earnings, which is another $45,000 they've taken off us."
Mr Roberts said he knew or had heard of seven or eight other farmers who also acted on Fonterra staff advice.
Dunedin lawyer Pieter Brits, of Rodgers Law, who is considering the merits of a class action, would not be drawn on how many people had contacted him.
"We are getting interest," he said when contacted.
He was still determining the facts and would then assess whether they had a legal claim.
The crucial point was what the farmers were allegedly told by Fonterra staff in relation to the share price.
He expected to make a decision on the case next week.
The independently valued share price has appreciated each year since Fonterra was formed, from $3.85 in 2001-02 to a peak of $6.79 before the May drop.
The issue has come to a head because Southern farmers now have the option of supplying alternative dairy processors, such as New Zealand Dairies at Waimate and Dairy Trust near Invercargill.
The new companies contract farmers to supply milk rather than requiring suppliers to be shareholders.
This allows Fonterra suppliers to cash in their shares if they shift to a competitor.
Dairy Trust, which will start processing in August, has 56 suppliers, and company management estimates 50 of those previously supplied Fonterra.
A Fonterra spokeswoman said the company would not comment, as it was "not appropriate to discuss individual shareholder matters through the media".
