So i recently acquire a Z500v from my friend (yeah i know its old and everything, but my other broke, and i need a quick fix), and i unlock it using the codes found on this site (originally locked to Vodafone). The phone unlocked fine and i can now successfully use a Tesco Mobile SIM in the phone, but the problem is, i can't use my Blyk SIM card in it. I can't really go back to Tesco Mobile, just because the phone don't work with Blyk, because I've just got used to not buying any airtime! (for those who don't know, Blyk is a network for 16-24 year olds where their SIM is topped up with 217 texts and 37 minutes each month, without any purchase of anything). When i put the Blyk sim card in, it just comes up SIM card failure and i can't do anything with the phone. Yes, i have tried the Blyk sim card in other phones and it works perfectly (even with much older models!)

Does anyone have any idea on what i could do to fix the problem!?

Thanks
Sam