requesting clarity on inconsistant salary amount every month

Dear Sir/madam,

i am working with a NGO at a senior level and since last one year my salary is not constant.
i have never got the actual salary as mentioned in my contract letter and also the TDS deduction is not constant every month.
After inquiry i have been told that TDS has been deducted every month which is a normal process.
I have faced issues because of such deduction particularly with financial institution as banks.

kindly let me know if such variance is normal or is there something else which I need to know.
please suggest the norms against which TDS is being deducted.
As per my knowledge TDS amount can be calculated at the begining of the financial year and total tax adjustment can be done during last quarter of the financial year so how this kind of deductions have been made.
Request you to give your precious time for my query.
looking forward for your response.



regards,