Tenant not ready to change the rent at current market rate

Hi Lawyers, I have rented out my property to a Public Sector Bank.Right now.The lease deed with the bank is renewed after every 10 years.We could not renew our rent in 2006 due to my family medical exigencies ,so still they are paying a meagre amount of 18 Rs/sqft. Now this time of renewal of lease deed in year 2016, I have asked them to renew rent at current market rate.But they told us that Bank is in stressed condition and couldn't offer more than 42 rs/sqft with 25% appreciation after every 5 years. We agreed at that statement .However in written they changed the offer to 42 rs/sqft with 20% appreciation after every 5 years.I dropped them registered letter to amend the appreciation rate it but I didn't receive any acknowledgement from neither Chief Manger or the General Manager. So after receiving no replies ,I sent them 3 letters on monthly basis asking them to vacate my property or change the rent also to current market rate.(The current market rate is around 80-100 rs/sqft in my area) However we agreed at that time because we trusted the Bank and they told us that bank is in pitiful condition right now and can't offer much. But now as Bank did not hold the terms discussed and now they don't even pick up my call to discuss it and they keep on delaying it. So I have declined the offer of 42rs/sqft with 25% appreciation and wish to get the rent at current market rate. Could you please advice me what could be done for it. Someone has asked me to solve it outside the court also because it is long and hard process and you might get a result in 5-6 years. Please advice what should be done to get a fast and fair fixation on rent