It seems you have paid for a W fare. Provided that the return portion is fully refundable you could get a refund and buy a o/w W for MFU. The fare quote is $998.10. The problem is availability. There is at least one seat available on August 5, then nothing until August 20 ex PHL. There is availability ex NYC every day beginning August 4 but the only EWR flight (not far from PHL) is the daylight service BA186. The fare there is $986.60 o/w. On August 5, BA188, sleeper service has some availability ex EWR and there is availability for some evening departure for the following few days. Depending on how many seats you are looking to MFU you might be in luck.