NS Call Option after cash only merger

When options are adjusted into cash-only, that means that you have an option on a fixed amount of cash rather than a fixed number of shares. The strike price remains the same, so your option is either in- or out-of the money and will not change (since the dollar amount is fixed). That's also why they're subject to early expiration. There's nothing about the option that's going to change between now and the original expiry date.

Assuming your contracts were for 100 shares, you now have an option to "buy" $700 in cash for $750 (strike of $7.5 per share * 100 shares in the original contract). Obviously you wouldn't do that, so your options are out-of-the-money and worthless. You don't get anything, but you don't lose anything either (other than the premium that you already paid.

When you have a merger for cash, existing common shares are converted into the right to receive $7.00 cash. Effective at the opening of the business day after the merger is consummated, option expiration is accelerated.

Calls with strike prices above $7.00 and puts with strike prices below $7.00 are then out-of-the-money and they are worthless. Since your calls are $7.50, you get nothing and your loss is what you paid for them.