You may be charged 10% extra for this service.

你可能会因此项服务而被额外收取10%的费用。

《柯林斯英汉双解大词典》

In case there is no indication of the extra service charges and the specified sum shall be regarded that the relative charges have been included in the price of the products.

如没有注明需额外收取服务费和服务费的数额，则视为有关技术服务的费用已包含在软件产品价格之内。

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Offer a special deal, extra service or a lower price during your trial/introductory period.

在此期间提供优惠，额外的服务或者低价。

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So whereas Ofcom proposes to free ITV1 to chase ratings, it wants Channel 4 to become, essentially, a second BBC, taking on extra public-service obligations.

ECONOMIST: Public-service broadcasting

The news coincided with the launch of Sky Go Extra - a service allowing users to download movies and TV shows so they can be watched offline.

BBC: Sky logo

On the other hand, if a franchisee insists he has to go above and beyond a brand standard to compete--say, by offering free broadband Internet service or extra pillows--Ledsinger has to know when to say okay. (Chains need to police the impulses to go up market, too, lest their other units suffer by comparison.) The warmth and fuzziness, he hopes, will trickle down.

FORBES: The Motelier