Exceeding plan limits with Optus can lead to additional fees, which depend on the type of service you have and the specific terms of your plan. For mobile plans, for example, exceeding your data allowance may result in either additional charges or the slowing down of your data speed until the next billing cycle. Home internet plans may also have data limits, and exceeding these may lead to excess usage charges or reduced speeds. However, some plans offer unlimited data options or data rollover features which may alleviate additional costs. It is always a good idea to check the specifics of your plan, which can be found on the Optus website. This information will provide clarity on any potential fees that could arise from exceeding usage limits.