Can I use a third party modem with MTNL Broadband in Mumbai

I am using MTNL Broadband in Mumbai with a Belkin wifi router and supplied Sterlite SAM300 AX modem. I have to pay 600 bucks annually for renting the modem. I want to buy a good but cheap modem without wifi to replace the existing modem which I wish 2 surrender to MTNL and save on costs. I have shortlisted 2 of them - TP-Link ADSL2+ Ethernet/USB Modem Router(TD-8817) and the D-Link ADSL 2+ Ethernet / USB Combo Router (DSL-2520U). Which one is more suitable for MTNL connection ? I am using the Belkin router 2 enable the wireless so that I can connect my laptop and cellphone for continuous net coverage. So if I use any of the above mentioned modem-router combo, do I have to disconnect my Belkin router as well ?

sterelite and beetle are just the finest modems out there in the market'

thnx Rishabh but again I see no point in renting one when I can buy the same one for 900 bucks.