The easiest solution is to have their address on file, and send them an actual letter to confirm the cancellation.
If you need to make you address pretty much free form anyway, it makes practically no difference to ask people to put their address including name. If you ask for a name, the problem is that the name they may want you to use in other contexts is not necessarily the same name that people they live with will recognise them by.
E.g. consider a trans person that want you to know them as one gender, but isn't out to their family.
The safest in general is to not ask for "just" a name, but ask "what should we call you in context X?" but in many cases you can forgo the name by not synthesising data items (such as an address) from multiple parts, but letting users provide the whole thing as one entity (you can still pre-populate based on most common patterns), which as a bonus saves you from other stupid mistakes.
To add to my previous comment, what if two or more people from the same address are signed up for your service? How would you help them distinguish between the correspondence each one gets from your company?
> To add to my previous comment, what if two or more people from the same address are signed up for your service? How would you help them distinguish between the correspondence each one gets from your company?
By asking "what should we call you when mailing you?" (if you insist on a name field) or "which address (including name) should we use when mailing you?" You could then if you wish pre-populate any variation of name you might have on file for them in those fields; the point is that the more you focus on gathering the specific information you need for that specific context, the fewer wrong assumptions you will be making about what the user would actually prefer.