Promotions won't apply and Ubereats offers zero support

Contact Us option in Ubereats app doesn't work, so there is no way to directly contact Ubereats for support. I eventually got the restaurant to ask Ubereats to contact me. However, when they phoned is was clear that they outsource support to a call centre that barely understands English and has no idea what they are doing. The manager, Syed, was extremely rude and kept talking over me and kept reading long tangents from their guidelines that had nothing to do with the issue I was enquiring about.