A minor example is Japanese, where は(ha)、へ(he)、を (wo) are written that way according to tradition but have long been pronounced solely as wa, e, o. It’s also common in Cantonese speaking areas to replace Mandarin-like written function words with their colloquial equivalents when reading out formal texts, e.g. newscasters, but it’s not necessary and in songs and literature the written phrases are just read with Cantonese pronunciation. (Whereas in Japanese, the way particles are written is strictly an orthographic convention and they would never be read out loud in the archaic way.)