If someone is unsure about the permissibility of a financial transaction involving interest or speculation, they should:

1. Research: Study Islamic finance principles regarding interest (riba) and speculation (gharar).

2. Seek Expert Guidance: Consult a knowledgeable Islamic scholar or financial advisor specializing in Shariah-compliant finance.

3. Evaluate Alternatives: Look for clearer, halal alternatives to avoid doubt.

If the information remains inconclusive, it’s best to avoid the transaction, as Islam encourages caution in doubtful matters (following the principle of wara’).