Threat of ejection from our property

Hello atty/s. Good day! I would like to seek legal help of the matter I am currently facing. About 15 years ago, my father was employed by a private company. We were settling near their business place. however, during their expansion, we were relocated to a village (wherein they own the land). So their agreement is that the company will deduct from his salary the monthly installment of our lot (which is about Php 400 only since the lot costs only 60,000 per their agreement). Years after, my father was terminated from work due to retrenchment, leaving about 40,000 of the balance unpaid until as of the moment. Months ago, the company sent us a letter that we must pay them the amount of 380,000 (appraised with 21% interest) for the 10 years of non-payment. We asked for consideration and they say we can settle it for 2Million pesos for 5 years instalment. I think the amount they are asking is already inequitable and unconsionable. please advise about possible actions or compromise. thanks! God speed.