Smartphone prices have fallen dramatically in recent years, and some of the most affordable handsets ever have launched in just the last couple of months. Microsoft unveiled its lowest-priced Windows Phone, the Lumia 435, just a few weeks ago, and some of its customers in India will soon be able to buy it for even less.

Microsoft India has announced a part-exchange program, allowing owners of its Asha feature phone range to trade in their handsets, in return for credit towards the purchase of a Lumia 435.

Microsoft Smart Exchange offers guaranteed credits towards the cost of the 435 when you hand over your Asha handset. Owners of the Asha 305, 306, 308, 309, 310 and 311 will get an 'assured discount' of Rs.1,000 INR; those trading in an Asha 500, 501, 502 or 503 will get Rs.1,500.

The Smart Exchange program will remain available until April 15, 2015, and the discounts on offer represent a saving of between 17% and 25% off the Lumia 435's standard retail price of Rs.5,999.

Users will also be able to enjoy Rs.1,250 of cashback (Rs.250 per transaction) of recharges via the Paytm app before April 15.