A clear description of what it is you are seeking and the package you have would better allow the community to help you.
More data is available on some plans as an automatic option (flex data) or on other plans by upgrading your package to one with higher data limits. I am not aware of a means to buy a bucket of data when you need or want it, though you might be able to switch plans up and down as your seasonal data needs change.
NFtoBC
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