Removing a cable blocker requires a special mdu tool that the cable guy uses on his tool belt. you some options to do this.
1. call the cable company and tell them to remove
2. of get the tool and do it yourself
all the tools are different so you need to know what you need. the most common is this little guy
http://www.newelectronx.com/proddetail.php?prod=n-usa-a
this is the tool that fits those locks on the grey boxes outside of your house or apartment.
removes rogers gilbert locking terminators and similar ones that look like that a bullet.
it might be a slam lock or star lock – with a funny pattern – in that case you need something like these little guys
http://www.newelectronx.com/proddetail.php?prod=n-usa-lq
http://www.newelectronx.com/proddetail.php?prod=n-usa-m
http://www.newelectronx.com/proddetail.php?prod=n-usa-p
or get the set if you dont know which you have
http://www.newelectronx.com/proddetail.php?prod=n-usa-set-b-d-j-k-l-m
hope this helps you out!