Compliance to follow after a breach of contract

we have signed contract with one datacenter for services, but in testing phase we found that bandwidth given to us for email services is very less, now to increase the bandwidth Data Center is asking for money. Since already we are paying them amount which is more then our other datacenter vendors. So we want to exit the contract. Now can somebody help me what are the compliances that my firm owes as per contract one month notice is needed, but we are start ups we cannt pay for one month without fulfilling of requirement. So we are feeling that we are forged by Datacenter, since we clearly mentioned our requirement then why they had offered us bandwidth of 3Mbps, when they have experience, they know that this bandwidth will not be useful to us. When now we want to exit the contract they say that they will take legal action etc. But I exited, we have no pending liabilities and dues, we have paid all our dues for services used. But they want us to pay for one month as we are exiting.