alterar plano

You use it just like in English. You can say tivemos que alterar o plano (we had to change the plan). It works for big life changes or just choosing a different pizza place. It is a very flexible collocation. You will often see it in the plural: alterar planos.

Use it when the weather ruins your beach day. Use it when a meeting gets moved. It is perfect for professional emails or texting your best friend. If you are at a train station and the track changes, you might hear this. It is the language of flexibility.

Don't use it for changing clothes or changing money. For clothes, use trocar de roupa. For money, use cambiar or trocar. Alterar plano is strictly for intentions and schedules. Using it for physical objects sounds a bit robotic and strange.

Portuguese speakers are known for being spontaneous. We call this 'jogo de cintura' (flexibility). Because of this, alterar planos happens a lot. It is not seen as rude if done with enough notice. In Brazil, plans are often 'fluid' until the very last minute. Being able to say you are changing plans is a survival skill.

You might hear mudar de planos which is even more common in casual talk. Trocar os planos is another one you will encounter. If the change is sudden, you might say mudar tudo. Alterar sounds slightly more polished than mudar, but both work perfectly.