Blocking service I pay for

When I got a contract with MTN I was told I can use the router anywhere. Now thar I took it on holiday it doesn't work and the reason given by MTN is that it can only be used at the adress where we live. I was led to believe that I can use it anywhere just for them to make the sale and now they are backtracking. Would like MTN to show.me exactly where the contract states I cannot use the router at any location I wish too. So in effect I am paying for a service I cannot use. It worked the first day and then stopped working. How can MTN block a service I pay for?