Bank statements don't match AP, AR transactions

We have a huge number of accounts to consolidate and we can't open different accounts for each operating unit. In short, dealign with banks is a centralized function from the head office and AR, AP is centralized too but on Oracle they are divided into operating units. This situation make the cash management module not functining at all. Please help.
This is an example of why implementation is a planning intensive task. Cash management relies on a series of setups in General Ledger. You indicate that you are having bank statement reconciliation problems.

The reconciliation process uses the basic accounting structure and various rules relating to how the various parts of the business inter-relate, as defined how the accounting structure maps between various businesses.

1. Review your basic accounting structure.
2. Review your hierarchies of values, and your rollup groups.
3. Review your flexfield cross validation rules.
4. Review your intercompany accounts
5. Review the transaction codes and setups for reconciliation as defined in your Cash Management setup.
6. Review the setup of your global consolidation system. This is the mapping rules which allow consolidation across all companies to one set of books.
7. Review your elimination sets (elimination sets reference accounts in one set of books).