(Story corrects timing of Herbalife analyst day.) NEW YORK ( TheStreet) -- In the wake of allegations made by hedge fund investor William Ackman of Pershing Square Capital Management that Herbalife ( HLF) in nothing more than a multi-billion-dollar pyramid scheme, the company said Monday it has hired investment bank Moelis & Co. as an adviser and will hold a meeting with analysts to rebut Ackman's comments on Jan. 10. The embattled health-supplements seller, which has received Ackman's scrutiny for its multi-level marketing sales arrangement, also said in a Monday press release that it has yet to use $950 million of a $1 billion five-year share-repurchase program authorized by its board because of "trading blackout period restrictions." The statement may address analyst questions on why Herbalife had been hesitant to launch a large buyback to flush out Ackman's short trade. Herbalife now says it expects to exceed its previously announced quarterly guidance of $50 million in share buybacks in coming quarters. The string of Monday announcements wasn't able to stem a share-price decline of almost 40% since Ackman disclosed to CNBC on Dec. 19 that he is short the company's shares and argued that its multi-level marketing arrangement is a pyramid scheme. In Monday trading, Herbalife shares fell over 4% to $26.06, bringing the 2012 loss to roughly 50%. Herbalife's Jan. 10 investor meeting will mark its formal rebuttal to Ackman's allegations and specifies that the company will detail a "comprehensive response to investor questions on its business model," in addition to color on "regulatory perspectives" and an "update on the business and strong growth prospects," the company said in the Monday press release. After CNBC's Dec. 19 report of Ackman's short, Herbalife Chief Executive Michael O. Johnson took to the network's airwaves shortly thereafter to mount a vigorous defense against allegations of a pyramid scheme, and called the short position "market manipulation." Johnson was unable to stem share losses that continued on Thursday as Pershing Square detailed the investment at the Ira Sohn Conference. "Herbalife is not an illegal pyramid scheme," the company said in a Thursday statement. Bullish Wall Street research analysts have also had little luck defending Herbalife from Ackman's short trade, which he told Bloomberg Television stands at over 20% of the company's outstanding shares. Previously, Herbalife said it would conduct an analyst day on the week of Jan. 7 to respond in detail to "the distorted, outdated and inaccurate information contained in Pershing Square's presentation."