Out-of-cycle mortgage interest rate increases, low deposit rates, closure of branches and higher fees have taken their toll on retail bank customer satisfaction levels, especially among customers of the Big Four.The latest Roy Morgan Research consumer banking satisfaction report shows the big banks' ratings have fallen to their lowest level since mid-2013. Over the 12 months to June the average ratings of the Big Four has fallen by 1.9 percentage points.The average rating of all financial institutions in the survey fell by 1.3 percentage points over the same period.National Australia Bank has suffered the biggest fall from grace - down 4.6 percentage points over the 12 months. Its satisfaction score of 78 per cent is the lowest among its peers.Commonwealth Bank has a rating of 81.2 per cent, ANZ 78.9 per cent and Westpac 78.1 per cent.Among the other financial institutions in the survey, Teachers Mutual Bank has the highest rating, with a score of 94.1 per cent, followed by Bank Australia (93.7 per cent), Heritage Bank (91.3 per cent) and ING Direct (89.8 per cent).Roy Morgan Research industry communications director Norman Morris said home loan customers were still recording satisfaction levels below those of non-home loan customers. This goes back to October and November last year when mortgage lenders made out-of-cycle rate increases.Morris said customers frequently mentioned fees and charges as a source of dissatisfaction. Reserve Bank figures shows that fees grew by 3.5 percent during the 2015 financial year to around A$12.5 billion.In recent years the growth in bank fees has been the result of increases in transaction volumes, for the most part. That was a factor last year but the RBA said there were also more increases in "unit fees". The rate of growth in fee income was the highest in three years.Morris said customers also raised the issue of branch closures.