You can switch off Chat for specific contacts or just a single time. Note, it's not possible to disable the whole feature.
1. Turn off Chat for contacts:
Inside the conversation, tap on the 3-dot menu and select 'Switch to sending SMS'.
2. Just a single time:
Inside the conversation, tap and hold on the 'send button'.
Note, when possible, Truecaller try to send a Chat to save your cost on SMS. We will automatically detect if a person is using Truecaller and use Chat instead.