Tds

Hello sir/ma'am, I have a query and i am confident enough that you would clarify my doubt. The thing is i recently joined an institution where i had to teach a particular subject, for 3 hours a day. At the time of joining they told me that i would get paid 10,000 rs per subject. I taught the same subject in 3 of their branches so as per the agreement the total amount which had to receive is rs 30,000. It took almost 50 days for me to complete the syllabus of that subject in all 3 branches. However at the time of payment, they deducted Tax deducted at source(tds) and paid me somewhere around 27,000 rs. As far as i know tds is deducted on salary but i don't think that getting paid for teaching PER SUBJECT can be considered as salary instead it could be termed as professional fees. And moreover i took 50 days to complete the subject syllabus so am being paid 27000 for 50 days and not for 30 days to term it as a salary. And as salary is paid periodically i am not sure that next time when will i teach there again as i finished my subject and i have to wait for the next batches to come to teach again and it would take more than 2 months for the next batches of students to come. In the meantime i am not earning anything. I am very confused on this matter please help me reach to a logical conclusion. P.S: When i asked my employer that i was promised to be paid rs 30,000 rs and at the time of joining they didn't told me anything about tds deduction so deducting tds is unfair they simply put aside my concern by saying that it is the government which is deducting it and i can reclaim my tds deduction by filling a form.