Get http://www.persmin.nic.in/WriteReadData/ATA/36033_5_2004_01April2005.htm Thsildar office asking if this document is being followed or not. They'll certainly answer in yes as they can not deny authority of that document.
I think there is some indepth interpretation is need in your case. Your father is working in Bank so ask Bank authority equivalent grade of your father at the time of joining and currently. If his equivalent grade at the time of joining is Class 3 then no issue. If that was class 2 and now he is class 1 officer (before age of 40 year) then you are in creamy layer. Equivalence can be inferred by your father's basic salary and its comparison with that of govt employees. You may get that equivalence certficate on Bank's letter pad.
In case no equivalence is decided then flat Income Test of 4.5Lakh will be applicable. I am putting explanation from above mentioned link. And also rule clearly state that income should exceed for last 3 consecutive year. Even if it is below 4.5 lakh even for a year in last 3 year (3 financial year so produce IT returns for last 3 year) the you won't be in creamy layer. Explain him all these. and even after that Tehsildar doesn't make your certificate ask him to reject your application in writing giving reason for cancellation. you may ten contact NCBC in delhi.
9. In regard to clause (ix) of para 4, it is clarified that the creamy layer status of sons and daughters of persons employed in organizations where equivalence or comparability of posts visà- vis posts in Government has not been evaluated is determined as follows:
Income of the parents from the salaries and from the other Sources [other than salaries and agricultural land] is determined separately. If either the income of the parents from the salaries or the income of the parents from other sources [other than salaries and agricultural land] exceeds the limit of Rs.2.5 lakh per annum for a period of three consecutive years, the sons and daughters of such persons shall be treated to fall in creamy layer. But the sons and daughters of parents whose income from other sources is also less than Rs.2.5 lakh per annum and income from other sources is also less than Rs.2.5 lakh per annum will not be treated as falling in creamy layer even if sum of the income from salaries and the income from the other sources is more than Rs.2.5 lakh per annum for period of three consecutive years. It may be noted that income from agricultural land is not taken into account while applying the Test.