Africa is a big place. For financial institutions, it's very different if you have moved to Central African Republic or Uganda vs moved to Mauritius or Morocco.
If your account is in otherwise good standing, they might just ask you to update your address and keep the account. Alternatively, they'll begin account termination, during which time usage of the account may be restricted but not frozen.
It's very unlikely they would freeze the money for simply neglecting to update your address.
However, if you have signed any statements saying you are still resident at your EU address, you may have committed some form of fraud. In that case, the bank might be more hostile. But even in that case, it's more likely they'll just terminate the account, not freeze money. For a bank, it's much easier to terminate an account than to freeze money. Far less paperwork.