Mobile phones

Because you will likely want a "Pay-as-you-go" plan, and you shouldn't be travelling too much, you might want to consider one of the new companies. They are a little more expensive at first - since you have to buy the phone - but then the monthly fees are usually less expensive AND you don't have to sign a contract. You just need to be careful that you don't use your phone when you are outside of the city, otherwise your rates get expensive.
There are also the BIG 3 telecoms. They usually want you to sign a 2 or 3 year contract, and it is VERY expensive to get out of a contract once you've signed the papers. They do have Pay-as-you-go plans though.
Whatever company you choose to go with, make sure you understand what you are paying for, what you are getting, and how long you are signing up for.