I'm not aware of any services that does that, you can try the following:

1. Create a topic in the services board (don't forget to mention the amount, site, etc.)
2. Contact shasan: https://bitcointalk.org/index.php?topic=5102555.0 (Not sure if he could pay it for you, but I usually exchange my BTC for his Skrill/PP).

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You didn't mention which service you're trying to pay, but if it's a known one, try to look into these sites, they might have gift cards that you could use.

Also, if the amount is lower than 50 GBP and credit cards are accepted, you can buy VCCs from Coinsbee and pay for the invoice as well.