Poor customer service & over-billing

When moving into our home we took out a contract with Chubb, to ensure security of our home. 3 months later faulty alarm signal started happening resulting in us getting atleast 3 calls a day. After the first week we realised it must be a fault, every call we got from Chubb we requested that someone from technical come check what the problem is. This was not done, we then cancelled the contract and got the confirmation of cancellation in February. 2months later they are still deducting money off my bank account. In March, April and May I called spoke to Anthea and the matter is still not resolved.