Dear Ms B.,
By law, all persons with income from employment that is subject to OASI may pay into pillar 3a. Substitute income, such as daily allowances from unemployment insurance (UI), also counts as income that is subject to OASI. Employees and self-employed persons who have an account with a pension fund can deduct a maximum of 6,768 Swiss francs from their taxes in 2017. For persons with income that is subject to OASI but no pension fund, this amount is 20% of their net earned income or a maximum of 33,840 francs.
Should you have neither earned income that is subject to OASI nor substitute income, you cannot benefit from all pension products. At Helvetia, for example, you can only pay into the flexible pension plan 3b but not into the tied pension 3a in this instance.
To address your specific situation in detail, I would suggest you contact a competent pension expert.