It would be like in English if someone says the "I took the fono to the storage but he didn't have batterons for it" when you mean "I took the phone to the store but he didn't have batteries for it" Without the correct-gendered article it sounds wrong, and sometimes it changes the meaning so it's a different word. But, if there's enough context often you can figure out what someone is trying to say. But, if you're the kind of foreigner who doesn't know the genders for common things, you also probably have a very strong accent and are making all kinds of other errors, like using the wrong articles, getting the word order wrong, etc.

In the end, a lot of it is about context and how else you're trying to communicate. Like, if you're holding the phone and say "fono" it will be obvious what you mean. If someone knows you were trying to get a replacement battery, then there will be enough context to understand batterons.

You will be understood, it will just give people a small pause.

Sometimes it may cause confusion, like "the phone (he) went through the washing machine (she) and now <she/he> is broken" changes meaning if you get the pronoun wrong. But then if you are used to disambiguate thIs kind of situation - and you have to in english - it shouldn't happen too often