If the contracts are under your name, you can regain control over them.

O2, Orange and Vodafone will all do whats called a "Sim Swap" Basically transfer the number and the service to another sim card, making the original one that your ex has inactive. Vodafone and O2 will do it in the shop, Orange over the phone. You just need to provide ID to prove youre the contract holder. Tell them your phone has been stolen (which it has been in effect) They will provide you with a new SIM, and barr the handsets your ex has so he will not be able to use them on any network.

You can then transfer your current PAYG number over to the contract (O2 and Orange only), or change the number by telling the network you are recieving abusive phone calls (they will only do this once).

The thing to remember is that the contracts are in YOUR name, so YOU have control over them.