Hi Inna,
Just chiming in to add a little context to what Peter said earlier.
Since your account isn't set up to use monthly invoicing the concept of a "budget" isn't applicable, so BudgetOrderService doesn't have a mechanism to know what value to return, so it just returns 0 as a default. Our team has said that this probably shouldn't be exposed at all, so for your purposes it's reasonable to ignore the value for spendingLimit.
Is there something you're trying to do with the API that this behavior is blocking? If so we can try to help with a workaround.
Best,
Ben, Google Ads API Team

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