National Australia Bank's reign as the major bank with the highest retail customer satisfaction rating has been short-lived. NAB climbed to the top of the pops in June for the first time since 2012 but has been knocked off by Commonwealth Bank in the latest Roy Morgan survey.According to the latest Roy Morgan Research consumer banking customer satisfaction report, NAB's rating fell 30 basis points to 81.9 per cent in August.CBA's rating rose by 30 bps to 82.6 per cent. Westpac's rating was down ten bps to 80 per cent and ANZ's was down ten bps to 79.4 per cent.Overall, Teachers Mutual Bank had the highest rating, at 94.8 per cent, followed by Victoria Teachers Mutual Bank (92.4 per cent) and GT Mutual Bank (91.5 per cent).Roy Morgan industry communications director Norman Morris said the high-value customer quintile (the 20 per cent of customers who account for 63.2 per cent of the value of retail banking services) were the least satisfied.High-value customers gave their banks an average rating of 78.2 per cent, compared with an average rating of 82.8 per cent from all bank customers.Among the big banks, NAB leads the way among high-value customers, with a rating of 77.5 per cent. It is followed by CBA (76 per cent), Westpac (75.1 per cent) and ANZ (73.3 per cent).Morris said: "With such a large and potentially profitable group being well below the average satisfaction level for each bank, they demonstrate the need for increased attention if overall satisfaction levels are to be improved."