There is a bit of a misunderstanding going on. H&M does not offer any credit card of their own. An H&M merchandise credit is not a credit card. A merchandise credit is like an H&M gift card, but serves a slightly different purpose. An H&M merchandise credit is like a store credit that is received when a standard refund cannot be issued. Customers may not be issued a standard refund when they return merchandise without a receipt or beyond the 30-day return period.
Although you may not be able to apply for a credit card directly from H&M, keep in mind that there are so many regular rewards credit cards that can allow you to benefit from your shopping. For example, you may choose the Discover it® Cash Back credit card. This card allows to earn up to 5% cash back at rotatating categories on up to $1,500 in purchases when you activate (you should register each quarter to earn rewards). Plus, 1% cash back on all other purchases. Also all the cash back you’ve earned will be matched at the end of your first year, if you are a new cardmember. You could turn $150 into $300. This card comes with no annual fee and with 0% intro APR on purchases (when the introductory interest rate is over, the ongoing APR will apply).