Methods or models to predict activity of clients of a bank?
Some keywords you might search for will be profiling, RFM, CRM and customer analysis.  clv (or customer lifetime value) might be your best keyword though.

An example CLV calculator: http://www.clv-calculator.com/customer-lifetime-value-formulas/clv-formula/

Here is an interesting clustering model: http://www.iieom.org/ieom2011/pdfs/IEOM068.pdf

An article on how surveys are used to classify customers: http://www.finreghq.com/articles/bank-customer-profiles-and-why-they-are-important-sample-profile-questions/

Again, a lot of good stuff if you search for banking and clv:

https://www.google.com/search?client=ubuntu&amp;channel=fs&amp;q=banking+clv&amp;ie=utf-8&amp;oe=utf-8