If you have friends or family in the UK, you're probably racking up your international call charges. If you need to compare or find the best rates for calling the UK, here's a comparison of three online phone card sellers.

Nobelcom calling card: Their lowest rate for calls to the UK is .9 cents with no connection fee. The $20 denomination will yield 2220 minutes and it's also rechargeable. There's a 99 cents maintenance fee per week though so you might want to use this in one sitting or you won't get the minutes that you paid for.

Enjoy Prepaid phone card: Enjoy Prepaid's lowest rate for the UK is 1.2 cents for calls to UK landline number and 12.4 cents to UK cell phone numbers. Their rounding is in 5 minute intervals compared with Nobelcom's 4 minutes. They also charge a maintenance fee and payphone surchages.

Banana call calling card: Banana call probably offers the cheapest rate at only .4 cents with their Banana Smile plan. There's a .99 cents connection fee though compared with the other two which is free. Rounding is at 8 minutes interval and weekly fee is higher at $1.49. Payphone and toll free surcharges also apply.

If you want to compare your own phone card with these three, be sure to take into consideration other charges as well so you know how many minutes they're really charging.