They can't force you to take another phone, no, but they can certainly refuse to repair the old one. You could try asking for a refund, but I'm not sure how much you'd get - almost certainly not the original value as you've had the phone for a year or two already. You may be better off just taking the N8/E7 and selling it, but you'd have to check on ebay prices and what Nokia would offer as a refund.