I am an Orange customer (have been since 1999) with a pay-monthly sim-only contract. I bought a new from Amazon in January. It worked fine until last Thursday. I found out on Saturday that the IMEI has been blocked, and I found out this morning that it is T Mobile that has blocked it.
The phone was brand new, and all seals were intact.
T Mobile are refusing to lift the block. They won't even tell me who blocked the phone, and are telling me to contact the retailer. Amazon can't lift the block, but have offered me a full refund if I send the phone back to them (at my expense!!)
It is disgraceful that T Mobile have caused me harm by recording inaccurate data on an IT system, and are refusing to correct it or assist me. I will be making a formal complaint to the Information Commissioner.