Cell C has asked law firm Bowmans to investigate business units possibly involved in 'irregular' practices after its debt rating was recently downgraded to reflect that a default had become a 'virtual certainty'. Shares in major shareholder Blue Label Telecoms plunged 15.1% to R3.31 in early trade a week ago, the worst level since 2008, BusinessLIVE reports. In late June, the stock was at R5.15. 'We have appointed attorneys Bowmans to investigate any parts of the business where we suspect that there may be irregular business practices and have also hired PwC to do a full procurement audit and review of our processes,' Cell C's interim CEO, Douglas Craigie Stevenson, said in a letter to stakeholders. 'Cell C has a zero-tolerance policy towards illegal or unethical activity and have encouraged employees to use the independent whistle-blowers service to anonymously report irregularities or illegal activities.'