Complaints about mobile phones to Australia\'s telecoms watchdog jumped nine percent in a year, accounting for two-thirds of all gripes received due to growing smartphone use, a study said on Monday. Telecommunications Industry Ombudsman Simon Cohen said there were 122,834 mobile phone complaints in the year to June 30 -- an increase of nine percent on the previous year -- despite overall grievances dropping two percent. 2 out of three complaints related to mobile phones, reflecting what Cohen said was the \"rising use of smartphones\". Some 89 percent of Australians were estimated to own a mobile phone in 2011 -- rising to 97-98 percent in the 18-44 age bracket -- with the market dominated by Internet-enabled handsets made popular by Apple and Samsung. Only Japan and South Korea are believed to have a greater level of 3G handset penetration, according to the government\'s Australian Communications and Media Authority. Sketchy coverage, over-charging and other bill disputes were the most common issues, with complaints about Internet usage charges rocketing 150 percent. Cohen said the number of complaints over credit blacklisting due to unresolved telecoms debts had also increased, which he described as concerning. \"Credit listings can have very significant impacts on people, affecting applications for credit, including for housing and personal loans,\" the ombudsman said. He also called for an improved system of notifying consumers when they are approaching a data or call limit, which will be required under a new telecoms consumer protection code to come into effect from 2013. \"Complaints about unexpectedly high bills and unnecessary financial over-commitment point to the urgent need for strong spend management rules, including those that are included in the new code,\" Cohen said.